50083

Powdercoating Galvaneal  

September 23, 2008

I have heard from some experts in the powdercoating industry that an iron phosphate pretreatment is unnecessary when powder coating galvaneal as long as it is sufficiently clean. It has been suggested that simply wiping any visible oil stains with thinner is acceptable. Our shop currently uses a 2 step iron phosphate process on all parts, including galvaneal. Could anyone advise weather skipping the phosphate process would be worth considering? Thanks.

Matt Arpin
Metal Fab/Finish Shop Manager - Biddeford, ME, USA

We have done extensive testing on galvanneal, and galvanizeed steel with respect to adhesion of powdercoating.
The conclusion is that both need a good competent pretreatment, of degrease, acid etch, zinc phosphate, seal. With at least one, preferably two rinses between each stage, one of them in demin.

Iron phosphate is of little value on zinc. (galvanneal or galv).

Alternatives to zinc phospate include Silanes, and other dry in place types of conversions.

Wiping with a rag before coating is common, we get at least a job a week sent to us to "do it properly", after someone else has done this, and the coating has failed. We strip it off and start afresh, as any overcoat still relies on that faulty coating to adhere.

Geoff Crowley    galvanizing &    powder coating shop Glasgow, Scotland

 

I'm usually pretty happy to see galvanealed material come through the door, but skipping basic good practice pretreatment when powdercoating any surface is a bad idea. Run it all through the wash tank!

Sheldon Taylor    supply chain electronics Wake Forest, No. Carolina