Metal finishing Q&As since 1989

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Paintability of electrogalvanized vs. galvannealed

2004

We perforate a wide variety of metals. We do not engineer our products to customer's applications, but we do offer advice. We currently have access to some light gage (.024" nom) lightly oiled electrogalvanized steel, excess prime. Being excess prime, we do not know the mill source. The application would require us to apply an additional lubricant, a petroleum hydrocarbon blend. The end use will primarily be security screens. Since we will be selling this product to a distributor, we do not know the exact end use. We are certain that many, if not all of the parts we supply will be painted, but do not know what cleaning/paint systems will be used. This product has been supplied by us in a galvannealed coating as well as a hot-dipped brite non-chem treat/light oil, as well as a Class 1 CQ cold rolled steel, all with success.

Will we be throwing the end-users a curve ball by supplying EG? I had heard that e.g., absorbs oil more than galvannealed, so is more difficult to degrease, resulting in paint adhesion problems. We've all seen the horrible paint peeling problems on automotive finishes of the '80's, which I understood was painted EG. I have also heard that with proper cleaning and surface prep, that e.g., has excellent paintability. We have asked our customer if subbing e.g., is OK, but they don't really know themselves. Or can we assume that a customer accustomed to painting galvannealed coatings will get the same performance from an electrogalvanized coating?

Thanks for any advice you can offer,

Ted Dohse
Industrial Perforator - Glendale Heights, IL, USA

The bad paint jobs in the 80s were from poor process and intolerant primer/topcoat combinations, not EG.

Your customers should not have any problem with e.g., over Galvannealed. They are both nicely paintable coatings, e.g., will need more careful cleaning due to the very deep surface profile, but there is not a lot of difference in the process.

Just be sure not to provide "passivated" galvanized metal to anyone wanting to paint. Without special consideration it is damned hard to get paint stuck to that.

Jeff Watson
- Pearland, Texas
2004