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My recollection is to the effect that the wash primer depends on a reaction with the base metal in order to function properly--something I think I read in the 'Coating Clinic' column in Products Finishing [link is to product info at Amazon] magazine; but I have no real knowledge of this subject.

Such Q&A columns tend to not be well-indexed in the databases for computerized literature searches, but a manual search should find it. If you have an associate in my area s/he is welcome to spend a few hours thumbing through my copies if you don't have a closer source of back issues, but another solution might be to contact the column's author, Carl Izzo, a consultant in Export, Pennsylvania.