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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.
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