Paints & Coatings Resource Center

Ask the Expert Question-and-Answer Archive

by Ron Joseph

October, 2005

Corrosion Protection at Steel - Aluminum Interface

Q. We are making an aluminum bus. However the chassis is made of steel. For the joints, we are painting a layer of chromate yellow primer (calcium carbonate 24% and magnesium silicate 20% barium sulphate 8.5%) on the surfaces joining. Is this a good corrosion prevention scheme? Do you have any other recommendations?

A. Applying a zinc chromate primer between steel and zinc is a good solution provided that you apply sufficient primer to prevent direct contact between the two metallic surfaces. The success of the primer does depend on the type of exposure the buses will see. In any case, I might be inclined to apply two coats of the primer. If the bimetallic couple (steel/aluminum) will be exposed to much humidity then you might want to look for an alternative non-metallic, non-conductive material that you can place between the two mating surfaces.


Ron Joseph

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