Galvanic corrosion automotive applications

Although originally intended for evaluation of nickel-containing decorative electroplated coatings, the Corrod-kote test, ASTM B 380, has been used to qualify the performance of galvanized products for automotive applications. Apparently, the chloride ions introduced in this process provide a useful indication of automotive underbody performance for products such as tubing for containment of automotive fluids and other small components. The Corrodkote test applies a corrosive slurry to the... 

Galvanic corrosion and the factors affecting it have been discussed in Chapter 20. However, a few precautionary comments are in order for aluminum, since it is anodic to most common materials of construction, with the exception of magnesium and zinc. In the presence of a good electrolyte, as little as 15 mV difference in corrosion potential of the two metals can have an effect, and if the difference is 30 mV or greater the anodic material will definitely corrode sacrificially to protect the contacting cathodic metal. A recently revised report on galvanic corrosion, with emphasis on automotive applications is available [73]. 

Sacrificial metals such as magnesium, zinc, and aluminum, are in the active region of the galvanic series and are extensively used for corrosion protection. The single largest application for cold-roll-bonded materials is stainless-steel-clad aluminum for automotive trim. The stainless steel... 

Galvanizing can be found in almost every major application and industry where iron or mild steel is used. The utilities, chemical process, pulp and paper, automotive, and transportation industries, to name just a few, have historically made extensive use of galvanizing for corrosion control. They continue to do so today. For over 140 years, galvanizing has had a proven history of commercial success as a method of corrosion protection in a myriad of applications worldwide. 

Unalloyed zinc also is a relatively soft metal having a low melting temperatme and a subambient recrystaUization temperatme. Chemically, it is reactive in a munber of common environments and, therefore, susceptible to corrosion. Galvanized steel is just plain carbon steel that has been coated with a thin zinc layer the zinc preferentially corrodes and protects the steel (Section 17.9). Typical apphcations of galvanized steel are familiar (sheet metal, fences, screen, screws, etc.). Common applications of zinc alloys include padlocks, plmnbing fixtures, automotive parts (door handles and grilles), and office equipment. 

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