Q. My company produces cold rolled steel equipment boxes for both interior and exterior use. Indoor boxes are fabricated from cold rolled steel and outdoor boxes are fabricated from hot dip galvanized steel. After we upgraded our finish system from alkyds to polyesters, we had problems on the hot dipped galvanized boxes in the form of blisters. Our metal pretreatment process for all products has the following five stages: hot alkaline cleaner, cold water rinse, hot 10% phosphoric acid, cold water rinse, warm water final rinse. The blistering only occurs on the hot dipped galvanized steel, not the cold rolled steel. What is causing our problem? C.F.
A review of available test methods, common applications and innovative instrumentation...
E-coat can produce uniform finishes with excellent coverage and outstanding corrosion resistance.
Specific questions about zinc phosphate and pretreatment are answered in one article...