Ask the Expert Question-and-Answer Archive

by Ron Joseph

April, 2004

What is the organic primer paint we finished in Z. Y. CHROMATE

Q. Can you explain in more detail about zinc yellow chromate? Do you mean that we first use Z.Y.P. THEN put some organic and do the salt spray. How much time will it test ? I was so confused about them? Christina Lee

A. Zinc chromatic pigment is a yellow colored dry powder. The pigment is mixed and compounded with resins and solvents to produce an industrial coating product used as a rust inhibiting primer where corrosion on metal is of major concern. Metal primers containing zinc chromate pigment are classified as one of the best primers for preventing corrosion and has the best rating for salt spray resistance among other oxide or phosphate primers. The zinc chromatic primers were used exclusively by the Department of Defense for preventing corrosion.

There are several military specifications that require the zinc chromate primer to be tested for salt spray resistance and to pass up to 1,000 hours of testing without any failure. The time that the zinc chromate primer will provide corrosion resistance depends on the resin in which it is dispersed and the type of topcoat that you apply. For instance, the combination of an alkyd zinc chromate primer followed by an alkyd topcoat will be considerably less than the salt spray exposure fror an epoxy zinc chromate primer followed by an epoxy topcoat. Therefore, if you want to know what type of salt spray resistance you can expect, you must be specific about the resin type. However, the zinc chromate pigment has been found to be toxic and harmful to the environment. In many areas it is unlawful to use chromate containing coatings.

Best wishes,

Tom Burke