plating, anodizing, & finishing Q&As since 1989
Primer Compatibility to Hot Dip Galvanized Surface
My corporation is currently having a problem with an assembly which is hot-dipped galvanized and subsequently painted. We have gone through an extensive analysis of the situation and cannot find a way to maintain adhesion of the paint without grit blasting prior to painting. For cost reasons, we would like to avoid grit blasting.
Assuming we have the process (galvanizing, cleaning, pretreatment etc.) correct and under control, one possibility that Amer. Galvanizers Association suggested is that our primer may not be entirely compatible with a zinc coating. Currently, we are using a MIL-P-53022 epoxy primer to coat the part. The contact at AGA implied that many paint manufacturers formulate primer/topcoats specifically for use on galvanized surfaces. Can anyone elaborate on this? Should we be concerned with using this primer on galvanized components? Thanks.Mark Thomas
- Oshkosh, Wisconsin
Hi, Mark. You say you have the "pretreatment" correct, but I'm wondering whether this refers to pretreatment before galvanizing or pretreatment before priming. Phosphate conversion coating is required between galvanizing and painting. Good luck.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
April 15, 2009
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