Ask the Expert Question-and-Answer Archive

by Ron Joseph

February, 2003

Acid Etch Primer for Zinc Chromate, Iron Phosphate

Q. What is the acid that is used in zinc chromate acid etch primer for use on galvanised steel? What is the effect of using such a primer on steel?

A.Generally the acid is a mild solution of phosphoric acid suspended in butyl alcohol. The purpose of the acid is to slightly etch the galvanized steel and also to deposit a very thin film inorganic iron phosphate onto the surface. The inorganic phosphate acts as a corrosion preventive and also provides the primer with a good adhesive base.