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8/2/2019 Corrossion Cavd Ppt
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According to the Federal Highway
Administration Corrosion costs U.S.Businesses an estimated $276 Billion
each year, or up to 6% of the nations
GDP.
The Cost Of Corrosion
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What is the root cause of this problem ?
What is the Science Behind Corrosion ?
What Strategies and technology can beImplemented to Control Corrosion ?
Three important Questions ?
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Without Corrosion protection will it
hold in a crash or fail ?
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Major Drive Components being
destroyed by Corrosion will cost you
money sooner than later.
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Moisture, severe temperatures, road debris ,sand,gravel and de-icing materials can sandblast vehicleunderbodies.
Once the paint coatings are chipped, even slightly,those areas are left exposed to the corrosiveenvironment.
De-icing compounds- Sodium Chloride, MagnesiumChloride and Calcium Chloride.
The Root Cause
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Rear FramesGussets
Rear Under ride guards
Threshold PlatesFront Aprons
Upper Couplers
Landing Gear Brackets and Braces
Front Under Structure
Suspension and Axle Assy.
Main Frame Assy.
Areas effected by Ice Melting Chemicals &Rock Impingement
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The chemical make up of Rust
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Fe(s) -> + Fe2+(aq) + 2e-
The electrons can move through the metallic iron to the outside of the
droplet whereO2(g) + 2H2O(l) + 4e
- -> 4OH-(aq)
Within the droplet, the hydroxide ions can move inward to react withthe iron(II) ions moving from the oxidation region. Iron(II) hydroxideis precipitated.
Fe2+(aq) + 2OH-(aq) -> Fe(OH)2(s)
Rust is then quickly produced by the oxidation of the precipitate
4Fe(OH)2(s) + O2(g) -> 2Fe2O3 H2O(s) + 2H2O(l)
The rusting of unprotected iron in the presence of air and water is theninevitable because it is driven by an electrochemical process.However, other electrochemical processes can offer someprotection against corrosion. For magnesium rods can be used toprotect underground steel pipes by a process called cathodic
protection.
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The presence of Salt greatly enhances the rusting ofmetals. This due to the fact that the dissolved saltincreases the conductivity of the aqueous solution
formed at the surface of the metal and enhances therate of electrochemical corrosion
The Science
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For more than 50 years ,sodium chloride (Rock Salt)has been used for De-Icing roadways.
Magnesium Chloride and Calcium Chloride havebecome popular options due to ease and speed ofapplication, as well as being effective at low
temperatures.
The Science
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CaCI2 and MgCI2 are especially destructive becausethey cling to the underbody of a vehicle andcrystallize as they slowly dry out.
These crystals are hydrophilic.
They absorb moisture keeping them in a semi-
solution state for extended periods of time, whichmultiplies their corrosiveness.
The Science
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Re-Design with Corrosion resistant materials.
and / or
Provide an effective and durable barrier to blockmoisture, salt and oxygen from reacting with the
steel surface.
The Quest for Answers
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Soft Film Barriers :
Galvanized Parts:
Aluminum Parts :Stainless Steel Parts :
Solutions to Consider :
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The most common soft film barriers consist ofThixotropic over based calcium sulfonate resin withcalcium carbonate platelets, and corrosion inhibitive
pigments.These are generally soft and highly surfactantcoatings that have a greater affinity to the substratethan to itself.
This allows self Healing and moderate creep back
of damaged areas.
Soft film barrier solution
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Advantages:
Relatively low cost,
More effective than alkyds, acrylics, enamels,
urethanes and epoxies in harsh environments
Remains soft and flexible
Effective at reducing corrosion undercutting
Soft film barrier solution
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Disadvantages:
Can be damaged by stone impingement
Low Gloss
Attracts dirt (discolors)
Remains somewhat sticky
Requires repair / recoating when damaged.
Soft film barrier solutions
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Galvanized, Aluminum, and Stainless Steel are veryeffective materials in the fight against Corrosion.
However Increased cost of using them can becomea competitive disadvantage in both manufacturingand replacing damaged parts.
Replacement Metals instead of Steel
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Galvanic Corrosion can become a factor whendissimilar metals come in contact with each other.
Are your good intentions of using Aluminum,Stainless or Galvanized along with steel actuallycausing corrosion?
Galvanic Corrosion
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There are three conditions that must exist for galvanic
corrosion to occur.
First there must be two electrochemically dissimilarmetals present.
Second, there must be an electrically conductive pathbetween the two metals.
And third, there must be a conductive path for themetal ions to move from the more anodic metal to the
more cathodic metal. If any one of these three conditions does not exist,
galvanic corrosion will not occur.
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Prevention: Manufactures andCollision RepairShops must give serious consideration to each of thefollowing possibilities of potential cross-
contamination and make every effort to prevent itfrom happening.
Galvanic Prevention:
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Provide separate areas where only aluminum isrepaired, away from steel vehicles where grinding,sanding, welding or other intensive repairs are
taking place.
Galvanic Prevention
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Consider a separate set of metal working tools usedexclusively for aluminum. As a minimum, clean allhammers, dollies, cutting tools, pry bars, etc.,
before and after using on aluminum.
Galvanic Corrosion Prevention
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Clean all sanding and grinding tools thoroughlyprior to use on aluminum. Always use newsanding/grinding disc, scuff pads, sandpaper, and
shop towels to avoid cross contamination.
Galvanic Corrosion Prevention
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When clamps are used, clean the jaws thoroughlybefore and after use on aluminum. The clampingarea should be wire brushed using a dedicated
stainless steel brush after removal of the clamp.
Galvanic Corrosion Prevention
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Suspension Protection
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Chassis application
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THANK YOU