Ask the Expert Question-and-Answer Archive

by Ron Joseph

Red Oxide Primer vs Zinc Chromate

Q. We are constructing a outdoor covered structure of trusses and columns of MS pipe. The roofing would be of MS coated sheet. Though the truss work will not be directly exposed to rain or sun, it will be exposed to varied weather conditions of heat and moisture. Which primer would be better, red oxide or zinc chromate and which paint should be the most suitable. Please let me know. Thanks.

A. Zinc chromate is preferable to red oxide. The highest performance coatings are epoxy primers followed by polyurethane topcoats, but these are expensive and you might not want to spend so much on the project. Your alternative is to apply an alkyd primer followed by and alkyd or acrylic topcoat.

Regards,

Ron Joseph