Home /
Search 🔍
the Site
pub Where the world gathers for
plating, anodizing, & finishing Q&As since 1989


Powdercoating Galvanneal

September 23, 2008

I have heard from some experts in the powder coating industry that an iron phosphate pretreatment is unnecessary when powder coating galvanneal 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 galvanneal. Could anyone advise whether skipping the phosphate process would be worth considering? Thanks.

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

September 25, 2008

We have done extensive testing on galvanneal, and galvanized 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 phosphate 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
Crithwood Ltd.
Westfield, Scotland, UK
crithwood logo

October 2, 2008

I'm usually pretty happy to see galvannealed 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
Sheldon Taylor
supply chain electronics
Wake Forest, North Carolina

finishing.com is made possible by ...
spacer gets replaced with bannerImages

Q, A, or Comment on THIS thread -or- Start a NEW Thread

Disclaimer: It's not possible to fully diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations might be harmful.

If you are seeking a product or service related to metal finishing, please check these Directories:

Chemicals &
Consult'g, Train'g
& Software

About/Contact    -    Privacy Policy    -    ©1995-2023 finishing.com, Pine Beach, New Jersey, USA