Galvanizing 2

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HOT-DIP GALVANIZING FORCORROSION PREVENTION:

A SPECIFIERS GUIDE


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CONTENTSCorrosion: What & Why . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Corrosion Concerns. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Metal & Alloy Corrosion .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

The Corrosion Process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Galvanic Corrosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Corrosion of Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Hot-Dip Galvanizing for Corrosion Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4History of Galvanizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Iron & Steel Protection Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Galvanizing Process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Surface Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Galvanizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Inspection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

The Metallurgical Bond . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Coating Thickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Design of Products for Galvanizing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Sizes, Shapes & Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Mechanical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Other Design Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Welding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Bolting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Painting Galvanized Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Environmental Compliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Economics of Galvanizing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Economic Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13First Cost. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Life-cycle Cost. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Cost-Per-Square-Foot-Per-Year Value Theory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Galvanizings Advantage as a Capitalized Expenditure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Cost Factors Associated with Other Corrosion-Control Methods . . . . . . . . . . . . . . . . . . . . . . . . 14Galvanizing vs. Painting: By the Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Galvanized Coatings Corrosion Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Atmospheric Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Chemical & Liquid Environments, Solution pH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Fresh Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Sea Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Other Metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Practical Uses of Galvanized Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Bridges & Highways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Power Generation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Transportation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24Water & Waste Water Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24Buildings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24Agriculture & Food Processing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Petrochemical & Chemical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Pulp & Paper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Original Equipment Manufacturing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

2002 American Galvanizers Association. The material in this publication has been developed to provide accurate and authoritative information about specifying hot-

dip galvanized products. This material provides general information only and is not intended as a substitute for competent professional examination and verification as to

suitability and applicability. The publication of the material herein is not intended as a representation or warranty on the part of the American Galvanizers Association.

Anyone making use of this information assumes all liability arising from such use.

Hot-Dip Galvanizing for Corrosion Protection - A Specifiers Guide


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CORROSION: WHAT & WHY?

What is corrosion? Most people would say that corrosion is rust. Thats thesimple answer, but scientists who study corrosion could answer in terms of complexchemical and physical processes; economists might sum up corrosion in dollars.

CORROSION CONCERNS

Corrosion costs in the United States totalnearly $300 billion per year according to areport by Battelle Columbus Labs, EconomicEffects of Metallic Corrosion in the UnitedStates.The report states, Approximately one-third of these costs could be reduced by broad-er application of corrosion-resistant materialsand the application of the best corrosion-relat-ed technical practices. The panel found thatprogress has been made in preventing corro-sion in some industries, especially motor vehi-cles. The study was first done in 1975; since

that time avoidable corrosion has been reducedfrom 40% to 35% overall, the study estimates.Avoidable corrosion still accounts for over$100 billion per year. Battelles report con-cludes that these costs could be reduced by abroader application of corrosion-resistantmaterials, improvements in corrosionprevention practice, and an investmentin corrosion-related research.

METAL & ALLOY CORROSION

In order to understand how gal-vanizing protects steel from corrosion,it is important to first understand cor-rosion. Metal corrosion generally isdefined as the undesirable deteriora-tion of a metal or an alloy. In otherwords, corrosion is an interaction ofthe metal with its environment that adversely affects the metals properties.

This definition does not address the specific types or causes of corrosion. Laterin this discussion it will be useful to make this definition more specific to the processof steel and iron corrosion.

THE CORROSION PROCESS

Metals rarely are found in their pure state. They almost always are found inchemical combination with one or more nonmetallic elements. Ore is generally anoxidized form of metal.

Significant energy must be input to reduce the ore to a pure metal. This energycan be applied via metallurgical or chemical means. Additional energy also may beinput in the form of cold-working or casting to transform the pure metal into a work-ing shape. Corrosion can be viewed as the tendency for a metal produced and shapedas a result of substantial energy input to revert to its natural, lower energy state. From

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1975 1997

All IndustriesTotal 82.0 300.0Avoidable 33.0 104.0

Motor Vehicles

Total 31.4 94.0

Avoidable 23.1 65.0

Aircraft

Total 3.0 13.0

Avoidable .6 3.0

Other Industries

Total 47.6 189.0

Avoidable 9.3 36.0

(Billions of Current Dollars)

Sources: Economic Effects of Metallic Corrosion in theUS, 1997, and Battelle estimates

Corroded bridge beam

Figure 1. Metallic corrosion in the U.S.


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a thermodynamic perspective, the tendency to decrease in energy is the main drivingforce for the corrosion ofmetals.

Corrosion of metals isan electrochemical process.That is, metal corrosion nor-mally involves both chemicalreactions and the flow of

electrons. A basic electro-chemical reaction that drivesthe corrosion of metals is gal-vanic action. In a galvaniccell, current is generatedinternally by physical andchemical reactions occurringamong the components of thecell.

GALVANIC CORROSION

There are two primarytypes of galvanic cells thatcause corrosion: the bimetallic couple and the concentration cell. A bimetallic couple(Figure 2) is like a battery, consisting of two dissimilar metals immersed in an elec-trolyte solution. An electric current (flow of electrons) is generated when the two elec-

trodes are connected byan external continuousmetallic path. A con-centration cell consistsof an anode and cath-ode of the same metalor alloy and a return

current path. The elec-tromotive force is pro-vided by a difference inconcentration of thesolutions contacting themetal(s). In a galvaniccell, there are four ele-ments necessary forcorrosion to occur:

Anode- This isthe electrode where theanode reaction gener-

ates electrons.Corrosion occurs at theanode.

Cathode- This is the electrode that receives electrons. The cathode is protect-ed from corrosion.

Electrolyte- This is the conductor through which ion current is carried.Electrolytes include water solutions of acids, bases and salts.

Return Curr ent Path- This is a metallic pathway connecting the anode to thecathode. It is often the underlying metal.

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Figure 2. Bimetallic couple

CONVENTIONAL

CURRENT

EXTERNALCIRCUIT

ELECTRONSELECTRONS

CATHODE ANODE

ELECTROLYTE

Figure 3. Arrangement of metals in galvanic series

CORRODED ENDAnodic or less noble

MagnesiumZinc

AluminumCadmium

SteelLeadTin

NickelBrass

BronzesCopper

Nickel-Copper AlloysStainless Steels (passive)

SilverGold

PlatinumPROTECTED END

Cathodic or most noble

Any one of these metals andalloys will theoretically cor-rode while offering protectionto any other which is lower inthe series, so long as both

are electrically connected.

In actual practice,however, zinc is by farthe most effective inthis respect.


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These four elements contribute to the basis of corrosion and corrosion prevention.Removing any one of these elements will stop the current flow and corrosion will notoccur. Substituting a different metal for the anode or cathode may cause the direction ofthe current to reverse, resulting in a change as to which electrode experiences corrosion.

It is possible to construct a table of metals and alloys listed in decreasing orderof electrical activity (Figure 3). Metals nearer the top of the table often are referred toas less noble metals and have a greater tendency to lose electrons than the more noblemetals found lower on the list.

CORROSION OF STEELThe actual corrosion process that takes place on a piece of bare mild steel is

very complex due to factors such as variations in the composition/structure of thesteel, presence of impurities due to the higher instance of recycled steel, uneven inter-nal stress, or exposure to a non-uniform environment.

It is very easy for microscopic areas of the exposed metal to become relativelyanodic or cathodic. A large number of such areas can develop in a small section of theexposed metal. Further, it is highly possible that several different types of galvaniccorrosion cells are present in the same small area of the actively corroding piece ofsteel.

As the corrosion process progresses, the electrolyte may change due to materi-als dissolving in or precipitating from the solution. Additionally, corrosion productsmight tend to build up on certain areas of the metal. These corrosion products do notoccupy the same position in the given galvanic series as the metallic component oftheir constituent element. As time goes by, there may be a change in the location ofrelatively cathodic and anodic areas and previously uncorroded areas of the metal areattacked and corrode. AsFigure 4 indicates, this eventually will result in uniform cor-rosion of the area.

The rate at which metals corrode is controlled by factors such as the electricalpotential and resistance between anodic and cathodic areas, pH of the electrolyte, tem-perature and humidity.

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Figure 4. Changes in cathodic and anodic areas

Mosaic of anodes and cathodes, elec-trically connected by the underlyingsteel.

Moisture in the air provides the elec-trical path between anodes and cath-odes. Due to differences in potential,electric current begins to flow as theanodic areas are consumed. Iron ionsproduced at the anode combine withthe environment to form the loose,flaky iron oxide known as rust.

As anode areas corrode, new materialof different composition and structureis exposed. This results in a change ofelectrical potentials and changes thelocation of anodic and cathodic sites.Over time, previously uncorrodedareas are attacked and uniform sur-face corrosion results. this processcontinues until the steel is entirelyconsumed.


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HOT-DIP GALVANIZING FOR CORROSION PROTECTION

Hot-dip galvanizing is the process of applying azinc coating to fabricated iron or steel material byimmersing the material in a bath consisting primarily ofmolten zinc.

The process is described in more detail later in this

guide. It is inherently simple, and this simplicity is a dis-tinct advantage over other corrosion-protection methods.

HISTORY OF GALVANIZING

The recorded history of galvanizing goes back to1742 when a French chemist named Melouin, in a presentation to the French RoyalAcademy, described a method of coating iron by dipping it in molten zinc. In 1836,Sorel, another French chemist, obtained a patent for a means of coating iron with zincafter first cleaning it with 9% sulfuric acid and fluxing it with ammonium chloride. ABritish patent for a similar process was granted in 1837. By 1850, the British galva-nizing industry was using 10,000 tons of zinc a year for the protection of steel.

Galvanizing is found in almost every major application and industry where ironor mild steel is used. The utilities, chemical process, pulp and paper, automotive, andtransportation industries, to name just a few, historically have made extensive use ofgalvanizing for corrosion control. They continue to do so today.

For over 150 years, galvanizing has had a proven history of commercial successas a method of corrosion protection in myriad applications worldwide.

IRON & STEEL PROTECTION METHODS

Barrier protection is perhaps the oldest and most widely used method of corro-sion protection. It acts by isolating the metal from the electrolytes in the environment.

Two important properties of barrier protection are adhesion to the base metal andabrasion resistance. Paint is one example of a barrier protection system.

Cathodic protection is an equally important method for preventing corrosion.Cathodic protection requires changing an element of the corrosion circuit, introduc-ing a new corrosion element, and ensuring that the base metal becomes the cathodicelement of the circuit.

Hot-dip galvanizing provides excellent barrier and cathodic protection.

There are two major variations of the cathodic method of corrosion protection.The first is called the impressed current method. In this method an external currentsource is used to impress a cathodic charge on all the iron or steel to be protected.

While such systems generally do not use a great deal of electricity, they often are veryexpensive to install.

The other form of cathodic protection is the sacrificial anode method, in whicha metal or alloy that is anodic to the metal to be protected is placed in the circuit andbecomes the anode. The protected metal becomes the cathode and does not corrode.The anode corrodes, thereby providing the desired sacrificial protection. In nearly allelectrolytes encountered in everyday use, zinc is anodic to iron and steel. Thus, thegalvanized coating provides cathodic corrosion protection as well as barrier protec-tion.

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Galvanizing steel grating


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GALVANIZING PROCESS

The galvanizing process consists of three basic steps:surface preparation, galvanizing and inspection.

Surface Preparation

Surface preparation is the most important step in theapplication of any coating. In most instances where a coat-ing fails before the end of its expected service life, it is dueto incorrect or inadequate surface preparation.

The surface preparation step in the galvanizingprocess has its own built-in means of quality control in thatzinc simply will not react with a steel surface that is notperfectly clean. Any failures or inadequacies in surfacepreparation will be immediately apparent when the steel iswithdrawn from the molten zinc because the unclean areas will remain uncoated.Immediate corrective action is taken.

On-site painting or other field-applied systems of corrosion protection mayinvolve the use of different subcontractors and/or work-groups to prepare the surface

and apply the coating. This can result in problems in coordinating activities, leadingto costly and time-consuming delays, errors and disputes concerning responsibilityand financial liability. Once a job has been delivered and accepted at the galvanizersplant, there is one point of responsibility for ensuring that the material leaves the plantproperly galvanized. That point of responsibility is the galvanizer.

Surface preparation for galvanizing typically consists of three steps: causticcleaning, acid pickling and fluxing.

Caustic Cl eaning- A hot alkali solution often is used to remove organic con-taminants such as dirt, paint markings, grease and oil from the metal surface. Epoxies,vinyls, asphalt or welding slag must be removed before galvanizing by grit-blasting,sand-blasting or other mechanical means.

Pickling- Scale and rust normally are removed from the steel surface by pick-ling in a dilute solution of hot sulfuric acid or ambient temperature hydrochloric acid.

Surface preparation also can be accomplished using abrasive cleaning as analternative to or in conjunction with chemical cleaning. Abrasive cleaning is a processwhereby sand, metallic shot, or grit is propelled against the steel material by air blastsor rapidly rotating wheels.

Fluxing- Fluxing is the final surface preparation step in the galvanizingprocess. Fluxing removes oxides and prevents further oxides from forming on the sur-face of the metal prior to galvanizing and promotes bonding of the zinc to the steel oriron surface. The method for applying the flux depends upon whether the particular

galvanizing plant uses the wet or dry galvanizing process.

In the dry galvanizing process (Figure 5), the steel or iron materials are dipped orpre-fluxed in an aqueous solution of zinc ammonium chloride. The material is then thor-oughly dried prior to immersion in molten zinc. In the wet galvanizing process, a blan-ket of liquid zinc ammonium chloride is floated on top of the molten zinc. The iron orsteel being galvanized passes through the flux on its way into the molten zinc. The fluxblanket is then pushed aside to allow for clean removal of the material from the zinc.

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Galvanizing structural angles


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Galvanizing

In this step, the material is completely immersed in a bath consisting of a min-imum 98% pure molten zinc. The bath chemistry is specified by the American Societyfor Testing and Materials (ASTM) in Specification B 6. The bath temperature is main-tained at about 850 F (454 C).

Fabricated items are immersed in the bath long enough to reach bath tempera-ture. The articles are withdrawn slowly from the galvanizing bath and the excess zincis removed by draining, vibrating and/or centrifuging.

The chemical reactions that result in the formation and structure of the galva-nized coating continue after the articles are withdrawn from the bath as long as these

articles are near the bath temperature. The articles are cooled in either water or ambi-ent air immediately after withdrawal from the bath.

Inspection

The two properties of the hot-dip galvanized coating that are closely scrutinizedafter galvanizing are coating thickness and coating appearance. A variety of simplephysical and laboratory tests may be performed to determine thickness, uniformity,adherence and appearance.

Products are galvanized according to long-established, well-accepted andapproved standards of the ASTM, the Canadian Standards Association (CSA), and the

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Figure 5. Galvanizing (wet process)

Eta(100%Zn)70 DPN Hardness

Base Steel159 DPN Hardness

Gamma

(75%Zn 25%Fe)250 DPN Hardness

Delta(90%Zn 10%Fe)244 DPN Hardness

Zeta(94%Zn 6%Fe)179 DPN Hardness

Figure 6. Photomicrograph of galvanized coating


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American Association of State Highway and Transportation Officials (AASHTO).These standards cover everything from the minimum required coating thicknesses forvarious categories of galvanized items to the composition of the zinc metal used in theprocess.

Testing methods and interpretation of results are covered in the publication TheInspection of Products Hot-dip Galvanized After Fabrication,published by the AGAand available from the AGA or your local galvanizer. This booklet includes a visualinspection guide that displays full-color, close-up

photographs.

THE METALLURGICAL BOND

Galvanizing forms a metallurgical bondbetween the zinc and the underlying steel or iron,creating a barrier that is part of the metal itself.During galvanizing, the molten zinc reacts with thesurface of the steel or iron article to form a series ofzinc/iron alloy layers.Figure 6is a photomicrographof a galvanized steel coating cross-section andshows a typical coating microstructure consisting of

three alloy layers and a layer of pure metallic zinc.Moving from the underlying steel surface outward,these are:

The thin Gamma layer composed of analloy that is 75% zinc and 25% iron,

The Delta layer composed of an alloy that is90% zinc and 10% iron,

The Zeta layer composed of an alloy that is94% zinc and 6% iron, and

The outer Eta layer that is composed of purezinc.

Below the name of each layer in Figure 6appears its respective hardness, expressed by aDiamond Pyramid Number (DPN). The DPN is aprogressive measure of hardness: the higher thenumber the greater the hardness. Typically, theGamma, Delta and Zeta layers are harder than theunderlying steel. The hardness of these inner layersprovides exceptional protection against coatingdamage through abrasion. The Eta layer is quite duc-tile, providing the coating with some impact resist-

ance.

The galvanized coating is adherent to theunderlying steel on the order of several thousandpounds per square inch (psi). Other coatings typical-ly offer adhesion rated at several hundred psi at best.

Hardness, ductility and adherence combine toprovide the galvanized coating with unmatched pro-tection against damage caused by rough handling during transportation to and/or atthe job site, as well in service. The toughness of the galvanized coating is extremelyimportant since barrier protection is dependent upon the integrity of the coating.

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Figure 7. Rust undercuts scratched paint

Figure 8. Zinc protects base steel even when scratched

Figure 9. Full corner protection provided


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Other coatings damage easily during shipment or through rough handling on thejob site. Experts will argue that all organic forms of barrier protection (such as paint)by their nature are permeable to some degree. Galvanized coatings are impermeable.

If the galva-

nized coating is

physically damaged,

it will continue to

provide cathodic pro-

tection to the exposed

steel. If individual

areas of underlying

steel or iron become

exposed as much as

1/4", the surrounding

zinc will provide

these areas with

cathodic protection

for as long as the

coating lasts.

Figure 7shows how corrosion will begin and immediately progress at a scratchor gap in a paint coating.Figure 8 shows how corrosion will be prevented at a scratchor gap in a zinc coating.

The galvanizing process naturally produces coatings that are at least as thick atthe corners and edges as the coating on the rest of the article. As coating damage ismost likely to occur at the edges, this is where added protection is needed most.Brush- or spray-applied coatings have a natural tendency to thin at the corners andedges.Figure 9 is a photomicrograph showing a cross-section of a corner of a galva-nized piece of steel.

Because the galvanizing process involves total immersion of the material, it isa complete process; all surfaces are coated. Galvanizing provides both outside andinside protection for hollow structures. Hollow structures that are painted (but not gal-vanized) have no corrosion protection on the inside.

The inspection process for galvanized items is simple and fast and requires min-imal labor. This is important because the inspection process required to assure thequality of many brush- and spray-applied coatings is highly labor-intensive and usesexpensive skilled labor.

Galvanizing continues at the factory under any weather or humidity conditions.Most brush- and spray-applied coatings depend upon proper weather and humidityconditions for correct application. This dependence on atmospheric conditions often

translates into costly construction delays.The galvanizers ability to work in any type of weather allows a higher degree

of assurance of on-time delivery. Working under these circumstances, galvanizing canbe completed quickly and with short lead times. A turnaround time of two or threedays for galvanizing is common.

COATINGTHICKNESS

ASTM, CSA and AASHTO specifications establish minimum standards forthickness of galvanized coatings on various categories of items. These minimum stan-dards are routinely exceeded by galvanizers due to the nature of the galvanizing process.

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Figure 10. Effect of silicon on coating thickness


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Factors influencing the thickness and appearance of the galvanized coating includechemical composition of the steel, steel surface condition, cold-working of steel prior togalvanizing, bath temperature, bath immersion time, bath withdrawal rate, and steelcooling rate.

The chemical composition of the steel being galvanized is very important. Theamount of silicon and phosphorus in the steel strongly influences the thickness andappearance of the galvanized coating. Silicon, phosphorous or combinations of thetwo elements can cause thick, brittle galvanized coatings. The coating thickness curve

shown inFigure 10 relates the effect of silicon in the base steel to the thickness of thezinc coating. The carbon, sulfur and manganese content of the steel also may have aminor effect on the galvanized coating thickness.

The combination of elements mentioned above, known as reactive steel to thegalvanizing industry, tends to accelerate the growth of zinc-iron alloy layers. Thismay result in a finished galvanized coating consisting entirely of zinc-iron alloy.Instead of a shiny appearance, the galvanized coating will have a dark gray, matte fin-ish. This dark gray, matte coating will provide as much corrosion protection as a gal-vanized coating having a bright appearance.

It is difficult to provide precise guidance in the area of steel selection withoutqualifying all of the grades of steel commercially available. The guidelines discussed

below usually result in the selection of steels that provide good galvanized coatings.

Levels of carbon less than 0.25%, phosphorus less than 0.04%, or man-ganese less than 1.35% are beneficial.

Silicon levels less than 0.03 % or between 0.15% and 0.25% are desirable.

Silicon may be present in many steels commonly galvanized even though it is nota part of the controlled composition of the steel. This occurs primarily because siliconis used in the deoxidization process for the steel and is found in continuously cast steel.

The phosphorus content should never be greater than 0.04% for steel that isintended for galvanizing. Phosphorus acts as a catlyst during galvanizing, resulting inrapid growth of the zinc-iron alloy layers. This growth is virtually uncontrollable dur-

ing the galvanizing process.

As the galvanizing reaction is a diffusion process, higher zinc bath temperaturesand longer immersion times generally will produce somewhat heavier alloy layers.Like all diffusion processes, the reaction proceeds rapidly at first and then slows aslayers grow and become thicker. Continued immersion beyond a certain time willhave little effect on further coating growth. In galvanizing reactive steels, the diffu-sion process significantly changes. Figure 10 shows the relative effect of increasedsilicon.

The thickness of the outer pure zinc layer is largely dependent upon the rate ofwithdrawal from the zinc bath. A rapid rate of withdrawal causes an article to carryout more zinc and generally results in a thicker coating.

ASTM, CSA and AASHTO specifications and inspection standards for galva-nizing recognize that variations occur in both coating thickness and compositions.Thickness specifications are stated in average terms. Further, coating thickness meas-urements must be taken at several points on each inspected article to comply withASTM A 123/A 123M for structural steel and A 153/A 153M for hardware.

DESIGN OF PRODUCTS FOR GALVANIZING

Corrosion prevention must begin on the drawing board. This is true regardlessof the system selected. Specifying galvanizing as the means of corrosion prevention

9


13/30

for a particular product has minimal design limitations. Certain practices should befollowed in designing structures for effective and safe galvanizing. These practicesare easily applied and in most cases are routine methods used to ensure maximum cor-rosion protection.

Most ferrous materials are suitable for galvanizing. These include cast iron,malleable iron, cast steels, hot-rolled steels, and cold-rolled steels. Structural steelshapes, including those of high strength, low alloy materials also are galvanizeable.Material with a tensile strength greater than 150ksi is susceptible to hydrogen embrit-

tlement in the standard galvanizing process. Prior knowledge of this steel property canbe handled by special cleaning processes to eliminate the embrittlement problem.Material with a tensile strength of 150ksi or less may be hot-dip galvanized after fab-rication to obtain the long-lasting protection afforded by the zinc coating. The mostsatisfactory way to ensure the safe, effective and economical galvanizing of articles isfor the designer, fabricator and galvanizer to work together before the product is man-ufactured. Please refer to the AGA publication The Design of Products to be Hot-DipGalvanized After Fabrication for further information.

SIZES, SHAPES & DIMENSIONS

Iron and steel articles to be galvanized after fabrication range from small pieces

of hardware to large welded steel assemblies or castings weighing several tons.Galvanizing kettles up to 40 feet long are available in most areas. It is common to findkettles approaching 60 feet. Through progressive dipping (sometimes called double-dipping - for articles too deep or too long to fit into the kettle), it is possible for thegalvanizer to process articles that exceed kettle dimensions. If you have questionsabout a products galvanizability, contact your galvanizer or the AGA.

MECHANICAL PROPERTIES

According to studies bythe BNF Metals TechnologyCentre in the United Kingdom

(as well as numerous othernational and international stud-ies), hot-dip galvanizing pro-duces no significant changes inthe mechanical properties ofthe structural steels or weldscommonly used throughout theworld. The galvanized articlesunderlying steel is chemicallyand metallurgically equivalentto the uncoated steels.

OTHER DESIGNCONSIDERATIONS

Galvanizing requires that cleaning solutions and molten zinc flow into, over,through and out of fabricated articles. Designs that promote the flow of zinc are opti-mal.

Filling and vent holes must be provided to prevent pickling or other cleaningbath fluids from becoming trapped in an article. It is best to avoid narrow gapsbetween plates, overlapping surfaces, and back-to-back angles and channels. Whenoverlapping or contacting surfaces cannot be avoided, all edges should be complete-ly sealed by welding but provided with a small hole or a short gap in the welding to

10

Figure 11. Bolt tension chart


14/30

relieve pressure build-up in overlapping areas thatexceed 12 square inches. See AGAs publicationRecommended Details for Galvanized Structures

for more information on this topic.

The Design of Products to be Hot-dipGalvanized After Fabrication is available from theAGA or your local galvanizer. In addition to cov-ering the essential considerations for proper design

and providing specific technical specifications anddetails, illustrations demonstrate both proper andimproper design practices. These practices are alsodescribed in ASTM A 143, A 384 and A 385.

WELDING

When welded items are galvanized, both the cleanliness of the weld area afterwelding and the metallic composition of the weld itself affect galvanizing quality andappearance. Some welding techniques that lead to good results include:

Use of an uncoated electrode where possible, Thorough removal of all welding flux residues if a coated electrode is used, A welding process that produces little or no slag, A submerged arc method for heavy weldments, Selection of welding rods providing a deposited weld that is composed of

the same materials as the parent metal, and Avoiding welding rods that are high in silicon.

Materials that have been galvanized may be welded easily and satisfactorily by allcommon welding techniques. The American Welding Society (www.aws.org, 800-443-9353) has produced a book that details all aspects of welding galvanized items.In general, anything that can be welded before galvanizing can be welded with rela-tive ease after galvanizing. A copy of the AWS recommended welding practices isavailable from the AGA or your local galvanizer.

BOLTING

Hot-dip galvanizing is a well-established and widely used process for coatingmechanical fasteners and welded joints. The prime mechanical fasteners used formaking field connections in steel are bolts that conform to ASTM A 307, A 325 andA 394 and are galvanized in accordance with ASTM A 153/A 153M and CSA stan-dards. Bolted galvanized structural joints can be designed for both bearing- and fric-tion-type connections. Galvanized joints of this type have an outstanding performancehistory. A wide variety of structures have been built using hot-dip galvanized steel andconnected using galvanized steel bolts.

Figure 11 shows a representative chart for bolt tension of galvanized versusblack bolts. A lubricated galvanized bolt can develop greater joint tension than that ofa black bolt. The bookBolted Galvanized Structural Joints is available from the AGAor your local galvanizer. It provides additional information on the characteristics andadvantages of bolted galvanized structures and offers comment on bolting procedures.

PAINTING GALVANIZED STEEL

Galvanized articles are easily and successfully painted. The two factors criticalto success are proper post-galvanizing surface preparation and proper paint systemselection. Galvanized steel is painted for a number of reasons: aesthetics, safety mark-ing and the desire for even longer lasting protection. Galvanizers must be informed if

11

An electrical substation utilizing aduplex system for identification


15/30

galvanized steel is to be subsequently painted so they can avoid applying a post-gal-vanizing treatment that would affect paint adhesion.

A corrosion protection system consisting simply of galvanizing provides long-term, cost-effective corrosion protection. Often the expected service life of the galva-nized coating actually exceeds the design life of the structure it protects. However, aduplex system, one consisting of properly selected and applied paint over galvaniz-ing, greatly extends the period that effective corrosion protection is provided. A use-ful rule of thumb is that a duplex system will provide effective corrosion protection

for one-and-one-half times the service life of the sum of the service lives of the in-dividual systems. For example, if the life of the galvanized coating in a particular en-vironment is 35 years and the expected service life of the paint system is 10 years, theexpected service life of the duplex system will be 67.5 years [1.5 (35+10)]. Whilesuch duplex systems often will have a premium first cost, they are usually the lowestlife-cycle cost solution. They may be the only feasible solution for structures inaggressive environments where later in-service painting is extremely difficult orimpossible.

The synergy of duplex systems in corrosion protection stems from three factors:

The paint film extends the life of the galvanized coating by providing addi-tional barrier protection to the zinc layers,

An underlying layer of zinc tends to prolong the life of a paint coating bypreventing an underlying layer of corrosion from developing, and

The corrosion products of zinc and its alloys further retard paint coatingdamage by sealing cracks and pores in paint films.

Some galvanizers do have facilities to shop-apply paint coatings after galvaniz-ing. The specifier should check with the galvanizer to determine if these facilities areavailable. When the design life of a fabricated item exceeds the service life of the gal-vanized coating without a duplex system, the initial galvanized coating can providesubsequent corrosion protection by adding a brush- or spray-applied paint system.When a paint-based corrosion protection system on bare steel reaches the end of itsservice life, abrasive blasting or grinding back to white steel is frequently necessaryin order to repaint. Preparation of a previously galvanized surface for a properlyselected paint-based system of corrosion protection is normally much simpler.

Two publications, Duplex Systems: Painting Over Hot-dip Galvanized Steel,andPractical Guide for Preparing Hot-dip Galvanized Steel for Painting, are avail-able from the AGA or your local galvanizer. They provide more complete and detailedinformation about duplex systems. In addition to providing a wealth of technicaldetails and a discussion of the suitability of a number of different types of paints forapplication after galvanizing, these publications also present a number of specificapplications and color photographs of duplex systems.

ENVIRONMENTAL COMPLIANCE

The United States Environmental Protection Agency (EPA), in addition to manystate and local environmental protection agencies, has established restrictions gov-erning volatile organic compounds (VOCs). Many brush- and spray-applied corrosionprotection systems contain VOCs and are thus subject to regulation. The galvanizedcoating contains no VOCs and is compliant with these regulations.

ECONOMICS OF GALVANIZING

12


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ECONOMIC ANALYSIS

Any exposed steel must be protected to ensure an effective service life. The costof corrosion protection for a structure will range from 0.5% to 5% of the cost of theproject. In exceptional cases, where a large area of lightweight steel is exposed to cor-rosive attack, the corrosion protection system may represent a much more significantpart of the project budget.

FIRST

COST

Looking at the two primary corrosion protection systems, galvanizing and paint,it is necessary to define the specifications for each so that a reasonable cost compari-son can be conducted. The galvanized material normally would be specified to ASTMA 123/A 123M. This calls for a minimum coating thickness of 2.3 ounces of zinc persquare foot of steel surface. Based on a 2001 survey of fabricators nationwide, thecost of the galvanizing component package in the fabricated steel price is approxi-mately $310 - $530 per ton depending upon the size, geographic area and type of proj-ect.

A high-performance paint system that is frequently specified in competition withgalvanizing consists of an inorganic zinc primer, a high-build epoxy intermediate

coat, and a polyurethane topcoat. This high-performance system, in order to functionproperly, must be applied over a steel surface that has been blasted to a Society forProtective Coatings (SSPC) specification of at least SP 10. Using the 1998 coatingseconomics survey published by the National Association of Corrosion Engineers(NACE) as a baseline for the estimated cost for shop application of this paint system,and a conservative average 5% increase per year (the 1979-1998 average), costs forthis paint system in 2001 are approximately $507 - $640 per ton.

These numbers indicate that galvanizing falls in the low end of the range of costfor the paint system. The difference in initial cost between the two systems is rela-tively insignificant when compared to the total project cost or life-cycle cost.

LIFE-CYCLE COSTBased on a moderate exposure to corrosive atmospheric elements, the galvanized

system will have a projected life (to 5% surface rust) in excess of 40 years. The paintsystem, based on the same NACE report, will require repainting approximately 11years from initial painting. Therefore, when designing a structure with an anticipatedlife of 40 years, it is necessary to include future costs of repainting as part of the totalcorrosion protection costs.

Maintenance painting consumes a significant and escalating portion of operat-ing and maintenance budgets. As more focus is placed on controlling maintenancecosts, a reliable, low-maintenance corrosion-protection system can be estimated byusing commonly accepted economic formulas.

COST-PER-SQUARE-FOOT-PER-YEAR VALUETHEORY

The current method for evaluating any coating system is to determine its cost indollars per square foot per year over the structures life. Concern with the cost of cor-rosion protection per square foot of steel has attracted significant attention amongspecifiers, engineers and corrosion consultants. The cost-per-square-foot-per-yearmethod seeks to minimize costs by analyzing all cost components including first cost,operating costs and maintenance costs. An economic analysis that includes both ini-tial costs and future maintenance costs should be used to select the most economicalprotective coating system. It is important to emphasize that in constructing a cost

13


17/30

compar i -son, eachs y s t e mmust beexaminedin detailfor possi-ble addi-t i o n a l

costs andsavings.

GALVANIZINGS ADVANTAGE AS A CAPITALIZED EXPENDITURE

Generally accepted accounting practices for building maintenance dictate thatmaintenance painting be considered an operating expense. The expenses of galvaniz-ing can be capitalized because these expenses generally occur during construction.

Under this accounting practice, galvanizing does not compete for precious operatingdollars.

COST FACTORS ASSOCIATED WITH OTHER CORROSION-CONTROL METHODS

A multitude of cost elements exist that typically are not included in an eco-nomic analysis:

Surface preparation in the field when repainting, Environmental compliance in the field when repainting, Downtime during painting operations, Containment systems,

Materials disposal, Weather delays, and Insurance and other unknown, uncontrollable factors.

These factors may cause the cost of repainting to accelerate well beyond theprojected cost as determined by the economic analysis. As a case in point, the Stateof Ohio Department of Transportation has projected a 43% increase in maintenancepainting costs in one year.

Galvanizing requires little if any maintenance in comparison to the maintenancedemands of paint systems. When all elements in the economic analysis are included,it is obvious that galvanizing has the lowest life-cycle costs.

14

Figure 12. Cumulative future maintenance costs


18/30

GALVANIZING VS. PAINTING: BY THE NUMBERS

The following example compares the costs of galvanizing with the costs ofpainting. The conclusion: galvanizing is a clear financial winner.

The Leaside Bridge, owned by Metropolitan Toronto, extends 1300 feet overthe Don Valley Parkway at Millwood Road and originally was built in 1927 usingpainted structural steel.

In 1969, it was decided that the bridge would be widened from four to six lanes.When bids were tendered, three different approaches were solicited:

Option 1:Blast-clean and paint all structural steel (specified as blast-clean,zinc-rich primer, and two-coat vinyl). Initial cost: $294,000

Option 2:Galvanize new steel in the expansion, and blast-clean and repaintthe bridges original steel in the field (same paint specifications asabove). Initial cost: $230,000

Option 3:Galvanize the new steel and zinc metallize the original steel. Initialcost: $271,000

The choice made was Option 2: galvanizing the new steel and repainting the

original steel, the lowest initial cost option. After more than 30 years in service inTorontos moderately industrial atmosphere, all the galvanized steel is in excellentcondition. Readings taken in 1995 showed a coating thickness of at least seven mils

15

Figure 13. Life of protection vs. thickness of zinc and type of atmosphere


19/30

of zinc. This ensures a further maintenance-free life of over 50 years for all galvanizedsteel on the Leaside Bridge. Galvanizing the new structural steel on the LeasideBridge saves the cost of repainting every 10 to 12 years.

The painted steel received a paint recoating in 1969 during bridge expansion.Another painting was done in the fall of 1980 and the summer of 1981. Localizedtouch-up painting was done again in 1991 and had already started to fail in 1997.

Figure 12 shows the cumulative estimated future costs for maintaining thestructure in 1969 dollars. The cost for the galvanized structure goes up little if anyduring the 80-year time period, but the cumulative dollars for the paint option growrapidly. Galvanizing saves money on the first cost and savings increase as long as thestructure exists.

GALVANIZED COATINGS CORROSION RESISTANCE

Galvanized coatings have a proven commercial history under numerous envi-ronmental conditions. The corrosion resistance of zinc coatings varies greatly with theenvironment in which they serve. In general, within range of most commonly encoun-tered environments, the galvanized coating corrodes at a rate between 1/10 and 1/30the rate of ungalvanized steel.

The predictability of the lifetime of a coating is important for planning andfinancing required maintenance. Measurements of the actual rate of consumption ofthe galvanized coating during the first few years of service often provide good datafor projecting remaining life until first maintenance. Due to the build-up of zinc cor-rosion products, which in most environments are adherent and fairly insoluble, thecorrosion rate may slow as time progresses.

Therefore, based upon measurements taken during the first few years of serv-ice, estimates of service life until first maintenance of a galvanized coating often willtend to be conservative.

Environments in which galvanized steel and iron commonly are used include

outdoor atmospheres, indoor atmospheres, hundreds of different chemicals, freshwater, sea water, soils, concrete, and in contact with other metals. Because of themany years galvanizing has beenused for corrosion protection, awealth of real-world, long-termexposure data on zinc coating per-formance in a wide variety of envi-ronments is available.

ATMOSPHERIC CONDITIONS

Zinc oxide is the initial corro-

sion product of zinc in relatively dryair. This is formed by a reactionbetween the zinc and atmosphericoxygen. In the presence of moisture,this is converted to zinc hydroxide.The zinc hydroxide and zinc oxidefurther react with carbon dioxide inthe air to form zinc carbonate. Thezinc carbonate film is tightly adher-

ent and relatively insoluble. It is primarily responsible for the excellent and long-last-ing corrosion protection provided by the galvanized coating in most atmosphericenvironments.

16

Figure 14. Effect of pH on corrosion of zinc


20/30

Since 1926, ASTM Committees A05 (Metallic CoatedIron and Steel Products) and G01 (Corrosion of Metals), andother organizations have been collecting continuous recordsof the behavior of zinc coatings under various categories ofatmospheric conditions. These atmospheric exposure testshave been conducted throughout the world to obtain corro-sion rate data for zinc exposed in various atmospheres.Precise comparison of the corrosion behavior of the galva-nized coating in various atmospheric environments is influ-enced by many factors. Such factors include the prevailingwind direction, type and density of corrosive fumes and pol-lutants, amount of sea spray, number of wetting and dryingcycles, and the duration of exposure to moisture. Althoughthere is a range in observed corrosion rates, actual observedrates rarely exceed 0.3 mils per year. It is also worthwhile tonote that when exposed indoors, the life of the galvanizedcoating will be at least two to three times that expected withoutdoor exposure in the same environment.

Figure 13 is a plot of the thickness of the galvanized

coating against the expected service life of the coating underoutdoor exposure conditions. This data is a compilation ofmany life tests of zinc-coated steel since the 1920s. Todaysatmosphere has substantially improved through anti-pollu-tion campaigns, so the data curves represent a conservativeportrayal of the life of zinc coatings in the 21st century. Theexpected service life is defined as the life until 5% of the sur-face is showing iron oxide (rust). At this stage it is unlikelythat the underlying steel or iron has been weakened or theintegrity of the structures protected by the galvanized coatingotherwise compromised through corrosion. Enough of thegalvanized coating remains to provide a good substrate for

17

Figure 15. Chemicals successfully stored in galvanized containers (partial list)

HydrocarbonsBenzene (benzole)Toluene (toluole)Xylene (xylole)CyclohexenePetroleum ethersHeavy naphthaSolvent naphtha

Alcohols

Methyl parafynol(methyl pentynol)

MorpholinoisopropanolGlycerol (glycerin)

HalidesCarbon tetrachlorideAmyl bromideButyl bromideButyl chlorideCyclohexyl bromideEthyl bromidePropyl bromidePropyl bromidePropyl chlorideTrimethlyene bromide

(1,3-dibromopropane)

BromobenzeneChlorobenzeneAroclors & Pyroclorschlorobiphenyls)

Nitriles (cyanides)Diphenylacetonitrilep-chlorobenzglycyanides

EstersAllyl butyrate

caproateformatepropionate

Ethyl butyrate

sobutyratecaproatecaprylatepropionatesuccinate

Amyl butyratesobutyratecaproatecaprylate

Methyl butyratecaproatepropionatesuccinate

Benzyl butyratesobutyratepropionate

succinateOctyl butyrate

caproate

Butyl butyratesobutyratecaproatepropionatesuccinatetitanate*

Propyl butyrateisobutyratecaproateformatepropionate

Iso- benzoateButyl butyrate

caproateIso- benzoatePropyl caproate

formatepropionate

Cyclohexyl butyrate*and other unspecified titanates

PhenolsPhenolCresols (mehtylphenols)Xylenols (dimethylphenols)Biphenol (dihydroxybiphenyl)

2,4-dichlorophenolp-chloro-o-cresolChloroxylenols

Amine and Amine SaltsPyridinePyrrolidineMethylpiperazineDicarbethoxypiperazine1-benzhydryl-4-methylpiperazine2-4-diamino-5-(4-chlorphenyl-6) ethyl-pyrimidine

Hydorxyethylmorpholine (hydrox-

yethyldiethylenimideoxide)p-aminobenzenesulphonylguanidineButylamine oleatePiperazine hydrochloride monohydrateCarbethoxypiperazine hydrochloride(dry)

AmidesFormamideDimethylformamide

MiscellaneousGlucose (liquid)Benzilideneacetonep-chlorbenzophenoneSodium azobenzensulphonateMelamine resin solutionsCrude cascara extractCreosoteChloroflourocarbons


21/30

implementation ofan appropriatelyselected brush- orspray-applied cor-rosion protectionsystem.

E x p o s u r eatmospheres may

be divided intofive types:

M od er a t el y

I n d u s t r i a l

Atmospheres -

These environ-ments generallyare the mostaggressive interms of corrosion.Air emissions may

contain some sulfides

and phosphates thatcause the most rapidconsumption of the zinccoating. Automobiles,trucks and plant exhaustare examples of theseemissions. Most city orurban area atmospheresare classified as moder-ately industrial.

S u b u r b a n

Atmospheres -Theseatmospheres are gener-ally less corrosive thanmoderately industrialareas and, as the termsuggests, are found inthe largely residential,perimeter communitiesof urban or city areas.

Temperate Marine

Atmospheres - Theservice life of the galva-

nized coating in marineenvironments is influ-enced by proximity to

the coastline and prevailing wind direction and intensity. In marine air, chlorides fromsea spray can react with the normally protective zinc corrosion products to form sol-uble zinc chlorides. When these chlorides are washed away, fresh zinc is exposed tocorrosion. Nevertheless, temperate marine atmospheres usually are less corrosive thansuburban atmospheres.

Tropical Marine Atmospheres -These environments are similar to temperatemarine atmospheres except they are found in warmer climates. Possibly becausemany tropical areas are found relatively far removed from moderately industrial areas,

18

Figure 16. Corrosion of zinc coated steel in selected natural freshwaters

Location and water

Gatun Lake, Canal ZoneTropical fresh water

Gatun Lake, Canal ZoneTropical fresh water

Pedro Miguel LocksPanama, Fresh water





River WaterHardness 7-6 (German)

River WaterHardness 7-6 (German)

Type ofZinc

Intermediate

Intermediate

Special highgrade

High grade

Intermediate

Select

Prime Western

99%zinc

99%zinc

Type ofTest

Immersion

Immersion

Immersion

Immersion

Immersion

Immersion

Immersion

ImmersionLab

ImmersionLab

Agitation

Stagnant

Stagnant

--

--

--

--

--

Still

Still

Corrosion ratemil/year

0.52

0.41

0.71

0.53

0.44

0.55

0.53

0.56

0.24

Figure 17. Corrosion of galvanized steel pipe in contact with avariety of soils

Nominal weight of coating - 3 oz/sq ft (915g/m2) of exposed area (a)

Soil Type

Inorganic Oxidizing Acid Soils

Cecil clay loam

Hagerstown loam

Susquehanna clay

Inorganic Oxidizing Alkaline Soils

Chino silt loam

Mohave fine gravelly loam

Inorganic Reducing Acid Soils

Sharkey clay

Acadia clay

Inorganic Reducing Alkaline Soils

Docas clay

Merced silt loam

Lake Charles clay

Organic Reducing Acid Soils

Carlisle muck

Tidal marsh

Muck

Rifle peat

Cinders

Cinders

Weight Loss (oz/ft) After Burial Period

2.1 yrs 4.0 yrs 9.0 yrs 12.7 yrs

oz/ft2 oz/ft2 oz/ft2 oz/ft2

0.3 1.4 0.6 0.6

0.3 1.2 0.7 0.6

1.0 2.3 0.9 0.8

1.1 2.3 1.6 1.1

1.6 3.3 1.1 1.1

0.6 1.5 0.7 1.1

3.3 -- 4.8 --

3.2 1.6 1.6 1.6

2.1 4.5 0.1 1.3

3.7 3.9 5.5 13.8

1.2 3.4 3.0 3.4

1.2 2.1 2.0 4.8

4.3 5.4 9.0 10.7

4.3 7.2 19.6 19.5

6.7 5.4 5.6 11.9

(a) This is weight of coating on one side of the pipe. 1 oz sq ft (305 g/m2) is equiva-lent to approximately 1.8 mil (43.7 um) thickness of coating.


22/30

tropical marine climatestend to be somewhatless corrosive than tem-perate marine climates.

Rural Atmospheres

-These are usually theleast aggressive of thefive atmospheric types.

This is primarily due tothe relatively low levelof sulfur and otheremissions found in suchenvironments.

CHEMICAL &LIQUID

ENVIRONMENTS, SOLUTION PH

A primary factor governing corrosion behavior of the galvanized coating in liq-uid chemical environments is the pH of the solution. Galvanizing performs well insolutions of pH above 4.0 and below 12.5 (Figure 14). This should not be considereda hard and fast rule, because factors such as agitation, aeration, temperature, polar-ization, and the presence of inhibitors also may change the rate of corrosion. Withinthe pH range of 4.0 to 12.5 a protective film forms on the zinc surface and the galva-nized coating protects the steel by slowing corrosion to a very low rate. The exactchemical composition of the protective film is somewhat dependent upon the specif-ic chemical environment.

Since many liquids fall within the pH range of 4.0 - 12.5, galvanized steel con-tainers are widely used in storing and transporting many chemical solutions.

19

Figure 18. Bond strength to concrete:black vs. galvanized reinforcing steel

1 3 12 1 3 12 1 3 12

Months of Curing

1000

800

600

400

200

0Stress

inP

ounds

persquare

inch

Source: Universityof California Black Galvanized

Study A Study B Study C

Figure 19. Comparison of epoxy-coated and hot-dip galvanized reinforcing steel bars

Comment Hot-Dip Galvanized Epoxy-Coated

1. Earliest use Early 1900s 1977

2. Requires care in handling No Yes

3. Can be dragged on ground Yes No

4. MUST be touched up No Yes

5. Has barrier protection Yes Yes

6. Has cathodic protection Yes No

7. Bond strength to concrete Excellent Poor

8. UV Resistance Good Questionable

9. After fabrication application Simple Difficult

10. Widely used Yes Yes

11. Cost Comparable Comparable*

12. Lead time 1-3 days 3 weeks

13. Availability of coating for other

embedded items Readily available Scarce

* Epoxy prices vary widely throughout U.S. and Canada and wide variations should be

expected.


23/30

Information concerning the specific corrosion behavior of zinc in more than 600chemical environments is presented inZinc: Its Corrosion Resistance, available fromthe AGA or your local galvanizer.Figure 15 (next page) shows an abbreviated list ofsome commonly used chemicals that are successfully stored in galvanized containers.

FRESH WATER

Galvanizing is successfully used to protect steel in fresh water exposure. Freshwater refers to all forms of water except sea water. Fresh water may be classified

according to its origin or application. Included are hot and cold domestic, industrial,

20

EN V I R O N M E N TAT M O S P H E R I C I M M E R S E D

METAL IN CONTACT RURAL INDUSTRIAL/ MARINE FRESH SEAURBAN WATER WATER

Aluminum and aluminum alloys 0 0 to 1 0 to 1 1 1 to 2

Aluminum bronzes and silicon bronzes 0 to 1 1 1 to 2 1 to 2 2 to 3

Brasses including high tensile (HT) brass 0 to 1 1 0 to 2 1 to 2 2 to 3

(manganese bronze)

Cadmium 0 0 0 0 0

Cast irons 0 to 1 1 1 to 2 1 to 2 2 to 3Cast iron (austenitic) 0 to 1 1 1 to 2 1 to 2 1 to 3

Chromium 0 to 1 1 to 2 1 to 2 1 to 2 2 to 3

Copper 0 to 1 1 to 2 1 to 2 1 to 2 2 to 3

Cupro-nickels 0 to 1 0 to 1 1 to 2 1 to 2 2 to 3

Gold (0 to 1) (1 to 2) (1 to 2) (1 to 2) (2 to 3)

Gunmetals, phosphor bronzes and tin bronzes 0 to 1 1 1 to 2 1 to 2 2 to 3

Lead 0 0 to 1 0 to 1 0 to 2 (0 to 2)

Magnesium and magnesium alloys 0 0 0 0 0

Nickel 0 to 1 1 1 to 2 1 to 2 2 to 3

Nickel copper alloys 0 to 1 1 1 to 2 1 to 2 2 to 3

Nickel-chromium-iron alloys (0 to 1) (1) (1 to 2) (1 to 2) (1 to 3)

Nickel-chromium-molybdenum alloys (0 to 1) (1) (1 to 2) (1 to 2) (1 to 3)

Nickel silvers 0 to 1 1 1 to 2 1 to 2 1 to 3Platinum (0 to 1) (1 to 2) (1 to 2) (1 to 2) (2 to 3)

Rhodium (0 to 1) (1 to 2) (1 to 2) (1 to 2) (2 to 3)

Silver (0 to 1) (1 to 2) (1 to 2) (1 to 2) (2 to 3)

Solders hard 0 to 1 1 1 to 2 1 to 2 2 to 3

Solders soft 0 0 0 0 0

Stainless steel (austenitic and other grades

containing approximately 18%chromium) 0 to 1 0 to 1 0 to 1 0 to 2 1 to 2

Stainless steel (martensitic grades

containing approximately 13%chromium) 0 to 1 0 to 1 0 to 1 0 to 2 1 to 2

Steels (carbon and low alloy) 0 to 1 1 1 to 2 1 to 2 1 to 2

Tin 0 0 to 1 1 1 1 to 2

Titanium and titanium alloys (0 to 1) (1) (1 to 2) (0 to 2) (1 to 3)

Key 0 Zinc and galvanized steel will suffer either no additional corrosion, or at the most only very slight additionalcorrosion, usually tolerable in service.

1 Zinc and galvanized steel will suffer slight or moderate additional corrosion that may be tolerable in some cir-cumstances.

2 Zinc and galvanized steel may suffer fairly severe additional corrosion and protective measures will usually benecessary.

3 Zinc and galvanized steel may suffer severe additional corrosion and the contact should be avoided.General notes: Ratings in brackets are based on very limited evidence and hence are less certain than other values shown.The table is in terms of additional corrosion and the symbol 0 should not be taken to imply that the metals in contactneed no protection under all conditions of exposure.Source: British Standards Institution, pp. 6484:1979, Table 23

Figure 20 . Additional corrosion of zinc and galvanized steel resulting from contact with other metals


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river, lake, and canal waters. Corrosion of zinc in fresh water is a complex processcontrolled largely by the impurities found in the water. Even rain water contains oxy-gen, nitrogen, carbon dioxide, and other dissolved gases, in addition to dust andsmoke particles.

Ground water carries microorganisms, eroded soil, decaying vegetation, dis-solved salts of calcium, magnesium, iron, and manganese, and suspended colloidalmatter. All of these substances and other factors such as pH, temperature and motionaffect the structure and composition of the corrosion products formed on the exposed

zinc surface. Relatively small differences in fresh water content or conditions can pro-duce relatively substantial changes in corrosion products and rate. Thus, there is nosimple rule or set of rules governing the corrosion rate of zinc in fresh water.

Water with relatively high free oxygen or carbon dioxide content is more cor-rosive than water containing less of these gases. Hard water is much less corrosivethan soft water. Under conditions of moderate or high water hardness, a natural scaleof insoluble salts tends to form on the galvanized surface. These combine with zinc toform a protective barrier of calcium carbonate and basic zinc carbonate. Figure 16indicates the service life of galvanized steel in various fresh waters.

SEA WATER

Galvanized coatings provide considerable protection to steel when immersed insea water and exposed to salt spray. The factors that influence the corrosion of zinc infresh water also apply to sea water. However, it is the dissolved salts (primarily sulfidesand chlorides) in sea water that are the principal determinants of the corrosion behaviorof zinc immersed in sea water. Given the high level of chloride in sea water, a very highrate of zinc corrosion might be expected. However, the presence of magnesium and cal-cium ions in sea water has a strong inhibiting effect on zinc corrosion in this type ofenvironment. One should be very skeptical of accelerated laboratory test results thatsometimes use a simple sodium chloride (NaCl) solution to simulate the effects of seawater exposure on galvanized steel. Real-world results often differ significantly fromaccelerated laboratory tests.

SOILS

More than 200 different types of soils have been identified and are categorizedaccording to texture, color and natural drainage. Coarse and textured soils, such asgravel and sand, permit free circulation of air, and the process of corrosion may close-ly resemble atmospheric corrosion. Clay and silt soils have a fine texture and holdwater, resulting in poor aeration and drainage. The corrosion process in such soils mayresemble the corrosion process in water.

The National Bureau of Standards has conducted an extensive research programon the corrosion of metals in soils. Some of their research on galvanized steel pipe datesback to 1924. The results shown inFigure 17are based on studies started in 1937 using

1 1/2" (38mm) steel pipe with a 3 oz. per square foot (5.4 mil) zinc coating. The tableshows annual metal loss in ounces per square foot in a number of soils tested. Data col-lected (but not displayed here) also show that the galvanized coating will prevent pittingof steel in soil, just as it does under atmospheric exposure. Even in instances where thezinc coating was completely consumed, the corrosion of the underlying steel was muchless than that of bare steel specimens exposed under identical conditions.

CONCRETE

Concrete is an extremely complex material. The use of various types of con-crete in construction has made chemical, physical and mechanical properties of con-

21


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crete and their relationship to metals a topic of ongoing studies. Steel wire or rein-forcing bars (rebar) often are embedded in concrete to provide added strength.

Rebar can be galvanized to retard corrosion, providing barrier and sacrificialprotection. As the corrosion products of zinc are much less voluminous than those ofsteel, the cracking, delamination, and spalling cycle is greatly reduced when usinggalvanized rebar. Laboratory data support, and field test results confirm, that rein-forced concrete structures exposed to aggressive environments have a substantiallylonger service life when galvanized rebar is used as opposed to bare steel rebar.

The bond strength between galvanized rebar and concrete is excellent. It oftentakes slightly longer to develop than the bond between bare rebar and concrete.However, according to laboratory and field tests, the bond between galvanized rebarand concrete is in fact stronger than the bond between bare rebar and concrete orepoxy-coated rebar and concrete (Figure 18).

A comparison of the qualitative and quantitative characteristics of galvanizedreinforcing steel and epoxy-coated rebar is shown inFigure 19. Information and addi-tional studies about the uses and behavior of galvanized reinforcement in concrete canbe found in Galvanizing for Corrosion Protection: A Specifiers Guide to ReinforcingSteel andRebar: A Processing and Inspection Guide for Quality Hot-dip GalvanizedReinforcing Steel, available from the AGA or your local galvanizer.

OTHER METALS

Where zinc comes into contact with another metal under atmospheric or aque-ous conditions, the potential for corrosion through a bimetallic couple exists. Theextent of the corrosion will depend upon the position of the other metal relative to thezinc in the galvanic series (Figure 3,pg. 2).

If an installation requires contact between galvanized materials and copper orbrass in a moist or humid environment, rapid corrosion may occur. Even runoff waterfrom copper or brass surfaces can contain enough dissolved copper to cause rapid cor-rosion. If the use of copper or brass in contact with galvanized items is unavoidable,

precautions should be taken to prevent electrical contact between the two metals. Jointfaces should be insulated with non-conducting gaskets and connections should bemade with insulating grommet-type fasteners. The design should ensure that water isnot recirculated and flows from the galvanized surface towards the copper or brasssurface, and not the reverse.

Under atmospheric conditions of moderate to mild humidity, contact between agalvanized surface and aluminum or stainless steel is unlikely to cause substantialincremental corrosion. However, under very humid conditions, the galvanized surfacemay require electrical isolation through the use of paint or joining compounds. Thegalvanic behavior of galvanized coatings in contact with various metals in atmos-pheric and immersion environments is summarized inFigure 20 (next page).

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PRACTICAL USES OF GALVANIZED STEEL

Corrosion of exposed steel is a major problem; galvanizing is an effective solu-tion to the problem. The previous chapters have explained the corrosion process, howgalvanized coatings are produced, and how well the coating prevents corrosion. Theremainder of this publication is dedicated to identifying the many applications of gal-vanizing in specific, real-world projects.

In each area, there are various photographs of applications. Additional detailed

information on the use of galvanizing for corrosion protection in these and otherapplications is available from the AGA or your local galvanizer.

23

Bridges & HighwaysBridge SuperstructureAnchor Bolts

Anti-suicide Rail

Base Plates

Bearing Assemblies

Bearing Plates

Bolts

Box Rail

Bridge Rail

Cable Connectors

CablesChannel Shear Connectors

Cross-bracing

Curb Angles

Diaphragms

End Dams

Expansion Dams

Finger Joint Expansion Dams

Floor Gratings

Flooring Grid

Girders

Guardrail and Posts

Inspection Catwalks

Jersey Barrier Embedments

Light PolesPipe Railing

Pipe Supports

Piping

Pot Bearings

Pour-in-place Forms

Reinforcing Splice Clips

Reinforcing Steel

Scuppers and Drains

Shear Studs

Sign Supports

Signal Light Poles

Spiral Shear Connectors

Splice Plates

Steel Divider BarrierStringers

Trench Drains

Bridge SubstructureAccess Doors

Bin-type Retaining Walls

Bolts

Catwalks

Drainage Supports

Drainage Systems

Driven Pilings

Fencing

Ground Anchors

Ladders

Pier Pilings

Reinforcing Splice Clips

Reinforcing Steel

Retaining Walls

Sheet Piling

Sign Supports

Temporary BridgesComplete Bailey Bridge

Structures

Insert Modules

HighwaysAnchor Bolts

Anti-suicide Rail

Base Plates

Box Rail

Break-aways

Culverts

Curb Angles

Delineators

Fencing

Gates

Guardrail and Posts

Jersey Barrier EmbedmentsLight Poles

Overhead Sign Supports

Pedestrian Overpass Bridge

Pipe Railing

Reinforcing Steel

Scuppers and Drains

Sign Supports

Signal Light Poles

Signal Supports

Sound Barriers

Steel Divider Barriers

Trench Drains

Power GenerationBuildingsBeams

Brick Ties

Brick Ledges

Columns

Dock Levelers

Equipment Supports

Girts

HVAC Supports

Lintels

Overhead Cranes

Purlins

Relieving Angles

Roof Hatches

Structural Steel

Yard EquipmentBollards

Bridges

Catwalks

Coal-handling

Equipment

Conveyor Supports

Corner Guards

CranesFencing

Flagpoles

Gates

Guardrail and Posts

Hopper Structures

Ladders

Mechanical Screens

Pipe Bridges

Pipe Supports

Railings

Reinforcing Steel

Sheet Piling

Sign Supports

Steel GratingSteel Stairs

Trench Covers

Truck Lifts

Truck Scales

Valve Stands

Power Transmission &DistributionAnchor Bolts

Bollards

Concrete Embedded

Reinforcement

Electrical Boxes

Equipment Supports

Faraday Cages

Fasteners

Fencing

Gates

Handrails

Ladders

Lattice Towers

Light Poles

Light Brackets

Pole Arms

Posts

Sign Supports

Steel Stairways

Fully galvanized Lizotte Bridg

Galvanized light pole

Galvanized structural panefor solar energ


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24

Transmission Poles

Tubular Towers

Walkways

Other Power Generation(Natural Gas, Hydroelectric,

Solar, Wind)

Anchor Bolts

Equipment Supports

Fencing

Fish LaddersFlood Control Gates

Flow Restrictors

Gas Turbine Skids

Generator Housings

Generator Support Platforms

Light Poles

Penstock

Platforms

Railings

Reinforcing Steel

Sheet Piling

Solar Panel Backs and

Supports

Solar Control Boxes

Tower Ladders

Tower Supports

Trash Racks and Booms

Windmill Towers

Transportation(Rail, Rapid Transit, Marine,

Air)

Advertising Shelters

Anchor Bolts

Anchorage Clips

Baggage Conveyor Supports

Ballast Stops

Bearing PlatesBenches

Bicycle Racks

Bollards

Brick Ledges

Brick Ties

Building Trim

Bulkheads

Cable Trays

Canopy Supports

Catenaries

Catwalks

Crash Barriers

Curb Angles

Decorative Emblem Supports

Dock Bumpers

Drain Pipes

Drains

Edge Angles

Electrical Boxes

Electrical Panels

Electrical Substation Framing

Exterior Stairway Systems

Fencing

Flagpoles

Floor Grating

Fountain Accessories

Gangplanks

Guide Rail

Handrails

Handicap Rail

Hangers

Ladders

Leveling Plates

Light Fixtures

Light Poles

Lightning Rods

Lintels

Manhole CoversMap/Sign Supports

Mesh

Ornamental Fencing

Ornamental Steel

Pilings

Pipe Sleeves

Post and Chain Fence

Pre-engineered Building

Exteriors

Pre-cast Hardware

Railings

Reinforcing Steel

Relieving Angles

Roof Hatches

Scuppers

Signal Bridges

Signal Equipment

Signal Structures

Sound Barriers

Stair Tread

Structural Support Steel

Tie Toe Plates

Trash Containers

Tree Grates

Tree Guards

Tunnel Liners

Utility Covers and Grates

Vehicle Washing Equipment

Walkway StructuresWindow Wall Supports

Window Washing Rails

Water & Waste WaterTreatmentAeration Tanks

Aerators

Anchor Bolts

Angles

Basin Wear-plates

Beams

Bollards

Brick Ledges

Brick Ties

Bridges

Catwalks

Channel Iron

Columns

Composting Equipment

Composting Conveyors

Conduit

Conveyor Supports

Dock Levelers

Embedded Frames

Fencing

Flagpoles

Floor Gratings

Floor Plates

Gates

Girts

Grit Chambers

Guardrail

Guardrail Posts

Guide Rail

HVAC Platforms

Ladders

Light PolesLintels

Mechanical Screens

Moving Structures

Overhead Bridge Cranes

Overhead Trusses

Pipe Bridges

Pipe Supports

Piping Hangers

Piping Rods

Pre-cast Veneer Hardware

Purlins

Reinforcing Steel

Relieving Angles

Scum Baffle

Scum Well

Skimmer

Steel Column Beams

Steel Doors

Steel Frames

Steel Grating

Steel Retaining Walls

Steel Stairs

Structural Steel

Transmission Towers

Truck Scales

Valve Stands

Weirs

BuildingsAnchor Bolts

Anchoring Clips

Architectural Panels

Attachment Devices

Atrium Supports

Balcony Rails

Beams

Benches

Bicycle Racks

Bleacher Supports

Brick Ties

Brick Ledges

Building System Frames

Canopy Supports

Catwalks

Columns

Crash Barriers

Curb Angles

Drain Pipes

Drains

Embedments

Equipment Screens

Fascia Support Steel

Fencing

Fire Escapes

Flagpoles

Galvanized steel is used exten-sively throughout Vancouverslight rapid transit system

Galvanized sound barrier

Galvanized components serve SanFrancisco Bay Area Rapid Transit System

Galvanized weirs


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25

Foot Bridges

Fountain Accessories

Garage Support Steel

Gates

Girts

Grating

Handicap Railings

Hatches

HVAC Supports

Integrated Steel Anchors

LaddersLeveling Plates

Light Fixtures

Light Poles

Lightning Rods

Lintels

Louvers

Manhole Covers

Metal Sculptures

Ornamental Steel

Pipe Bollards

Pipe Hangers

Playground Equipment

Post and Chain Fence

Pre-cast Hardware

Purlins

Railings

Relieving Angles

Roof Trusses

Scuppers

Security Gates

Sign Posts

Stadium Seating

Stair Stringers

Sun Screens

Trash Containers

Tree Grates

Tree Guards

Trellises

Utility CoversWindow Washing Rails

Window Wall Supports

Agriculture & FoodProcessingBuilding Structures

Conveyor Casing

Electrical Conduits

Equipment Hooks

Equipment Supports

Farm Buildings

Farm Implements

Fasteners

Feeding Equipment

Fencing

Gates

Grain Conveyors

Grain Drying Equipment

Grain Elevators

Grain Hoppers

Grain Mixing Equipment

Grating

Growing Racks

High-speed Freezing

Equipment

Irrigation Equipment

Light Poles

Meat Conveyors

Panels

Power Take-off Shifts

Pre-engineered Buildings

Processing Equipment

Railings

Refrigeration Brackets

Refrigeration Shelves

Side Frames

Silo Extraction EquipmentSlotted Floors

Stanchions

Steel Bands

Substation Structures

Supporting Structures

Tractor Parts

Trailers

Transmission Poles

Truss Plates

Vegetable Washing Machines

Veterinary Equipment

Waste Conveyor Systems

Waste Handling Equipment

Pumps

Watering Troughs

Wheel Tractor Hubs

Window Frames

Petrochemical & ChemicalAmbient Temperature Ducts

Anchor Bolts

Beams

Belt Guards

Cathodic Protection Rectifiers

Catwalks

Checkered Plate

Cogeneration Equipment

ColumnsConveyor Systems

Cooling Tower Structure

Crane Supports

Cross-bracing

Decks

Drain Pipes

Drive Piling

Electrical Cable Ducts

Electrical Conduits

Embedded Items

Equipment Guards

Equipment Screens

Fasteners

Fencing

Fire Extinguishing Equipment

Flare Towers

Flat Plates

Girts

Gratings

Handrails

Heat Exchanger Tubing

Ladders

Marine Terminal Structures

Off-shore Structures

Outside Switch Gear Frames

Pipe Bridges

Pipe Racks

Pipe Supports

Pipeways

Platforms

Precipitator Structure

Prefab Building

Structures

Process Equipment Skids

Process Piping

Process Vessels

Purlins

RailingsSafety Equipment

Sag Rods

Scuppers

Stairways

Stringers

Transmission Poles

Walkways

Waste Water Treatment

Equipment

Pulp & PaperAnchor Bolts

Benches

Bleach Plant StructuresBoiler Recovery

Structures

Bollards

Bolts

Brick Ledges

Brick Ties

Cable Tensioning Clips

Cable Trays

Canopy Supports

Catwalks

Conduit Bridges

Conveyor Assemblies

Conveyor Supports

Crane Support SteelCranes

Cross-braces

Curbing Angles

Dam Gates

Dock Levelers

Drain Pipes

Drive Piling

Electrical Conduits

Electrical Penetration

Seals

Elevated Tank Platforms

Equipment Bridges

Equipment Screens

Fencing

Fire Extinguisher Piping

Fire Escapes

Fire Ladders

Flagpoles

Floor Seals

Floor Support Steel

Foot Bridges

Gas Substations

Gates

Girts

Gratings

Guardrail

Handrails

The White House has paintgalvanized steel security gat

Galvanized pre-engineerbuild

Galvanized walkways and railinprovide long-term serv

Galvanized petrochemical plan


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26

Hangers

Hatch Covers

HVAC Support Steel

Kick-plates

Leveling Plates

Lighting Towers

Lightning Rods

Lime Kiln Structural

Steel

Lintels

LouversManhole Covers

Microwave Towers

Non-insulated Pipe

Bridges

Pipe Bridges

Pipe Sleeves

Pipe Stanchions

Plates

Platforms

Pollution Control

Structures

Power Distribution

Towers

Power Line Transmission

Towers

Power Substations

Pre-engineered Structures

Purlins

Reinforcing Mesh

Reinforcing Steel

Relieving Angles

Roof Hatches

Safety Cages

Safety Guards

Safety Railings

Scale Equipment

Screen Room Structural

Steel

ScuppersSheet Piling

Sign Supports

Stack Supports

Stair Stringers

Stairways

Steel Pipe

Structural Steel

Tank Supports

Trash Containers

Trash Racks

Trench Edging

Tunnel Liners

Utility Covers

Vehicle WashingEquipment

Waste Water Digesters

Support Steel

Window Washing Rails

Wood Yard Conveyor

Structures

Original EquipmentManufacturingAmusement Rides

Antennas

Bicycle Racks

Boat Anchors

Boat Stabilizers

Boat Trailers

Bolts

Buckets

Cable DrumsCable Trays

Car Parts

Cellar Doors

Conduit

Cooling Tower Parts

Dock Hardware

Dock Levelers

Dumpsters

Electrical Enclosures

Fencing

Flagpoles

Frames

Garbage Cans

GratingGuardrail

Handrails

Hardware Items

Industrial Trolley Caster

Frames

Light Brackets

Light Duty Vehicle Ramps

Light Poles

Microwave Mounts

Nails

Net Reels

Park Benches

Picnic Table Frames

Pipe HangarsPortable Building Frames

Refrigeration Brackets

Refrigeration Shelves

Scaffolding

Scales

Security Cage Frames

Security Gates

Spiral Staircases

Storm Shelters

Towers

Trailer Door Hardware

Trash Receptacles

Truck Parts

Utility Trailers

Wheelbarrows

Galvanized boiler plant

Galvanized pipe bridge

Galvanized support part for floating dock

Galvanized ski lift tower


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American Galvanizers Association6881 South Holly Circle, Suite 108

Centennial, Colorado 80112Phone: 800-468-7732

Fax: 720-554-0909www.galvanizeit.org

Documents

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