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Design & Fabrication

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Design & Fabrication

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Materials Suitable for

Hot-Dip Galvanizing

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Hot-Dip Galvanized Fasteners

Hot-dip galvanized

fasteners are

recommended for joiningHDG structurals

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The Galvanizing Reaction

Click to play animationFlash Player Required

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Typical Zinc-Iron

Alloy Layers

IrregularZinc-IronAlloy Layers

Coating Microstructures

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Steel Reactivity

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Coating Growth

Other factors that effect the growth of the

coating

Other chemical components of steel besidessilicon:

Phosphorus

Manganese

Steel Surface Roughness

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Appearance of HDG

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Combining Different Materials

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Dissimilar Thicknesses

Different thickness

Zinc bath

temperature at

different times

Similar thickness

Maintain original

shape

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Weld Rod Chemistry

Just as the base steel

chemistry influences

coating growth, so

does the chemistry of

the weld rod.

Si < 0.04% or

0.15 < Si < 0.22

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Welding Procedures

& Flux Removal

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Seal-welding

The viscosity of

molten zinc prevents

it from entering gaps

of 3/32 and smaller.

Solutions used to

clean the steel can

penetrate small gaps

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Welding after Galvanizing

American Welding Society

Remove coating 2-4 away from weld area

Repair area using ASTM A 780

Welding Galvanized Steel

Slower welding speeds, higher energy input

Damage galvanized coating in the Heat-Affected Zone (HAZ), repair is necessary

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Cold-Working

Severe cold-workingof steel increases thelikelihood for strain-

age embrittlement.ASTM A 384

Keep bend radii aslarge as possible, butat least 3 times thesection thickness

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Galvanizing Oversized Pieces

Progressive Dipping

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Material Handling

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Venting & Drainage

Cropped Corners

(Preferred)

Holes Close to Corners

(Alternatively)

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Cropped Corners

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Venting & Drainage: Base Plates

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Venting & Drainage

VentDrain

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Venting & Drainage: Tanks

Vent diagonally opposite fill hole

Cropped internal baffle (top & bottom)

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Venting & Drainage: Tanks

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Examples of Good Tank Design

Good

Design

Poor

Design

Flush interiors

provide gooddrainage

TrappedZinc

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Minimizing Distortion

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Temporary Bracing

Large diameter, thin-walled pipe may require

temporary bracing to prevent possible distortion.

Temporary Bracing

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Castings

Castings usually

require some form of

mechanical cleaning

to remove

encapsulated sand

particles from

crevices.

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Marking

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Masking

Compound used to prevent the galvanized

coating from forming in certain areas of the steel

(a.k.a. stop-offs)

Threads

Areas to be welded

Studs

Not 100% effective and adds significant labor inapplication and removal after galvanizing