Ask the Expert Question-and-Answer Archive

by Ron Joseph

April, 2006

Zinc Chromate Primer

Q. To what temperature and humidity level can zinc chromate primer be painted in a machine in order to avoid corrosion?

A. Zinc chromate primers are designed to prevent corrosion under humid conditions. However, if the primer will be exposed to high humidity for long periods, or continuously, you should apply two coats of primer followed by an intermediate and topcoat to prevent humidity from penetrating the paint film.

Alternatively, you might consider a completely different primer, such as an inorganic zinc rich primer.

The temperature to which the primer can be exposed depends on the resin system. For instance, alkyds can only tolerate moderate temperatures, while some epoxies can tolerate higher temperatures. Most organic coatings should hot be exposed to temperatures above 300oF for lengthy periods.

Best wishes,

Ron Joseph