Surface Variations in Body Steels as a Parameter of Automotive Primer Performance 650514
Leithauser demonstrated that lead contamination on steel causes premature corrosion failure when steel is phosphate treated. We postulate that such failure results from oxidation of lead to plumbous ion with subsequent formation of soluble lead phosphate causing blistering by water absorption, and that it can be minimized by forming insoluble zinc chromate.
Addition of zinc chromate to automotive primers effects improvement in corrosion resistance if the zinc is tied up by free acid. This acid can be part of the vehicle or can be post added where a nonacidic vehicle, for example, hydrocarbon resins, is used.