Home /
Search 🔍
the Site

Chime right in! (no registration req'd)


""Cratering" after cataphoretic painting on galvannealed steel"


Hello everyone,

Could anyone explain me why when we paint galvannealed steel (steel with a zinc-iron alloy) in a cataphoretic line, appears sometimes "cratering". Can the quantity of iron in the alloy affects, or there are other reasons, like impurities from the manufacturing process of the steel, produce this surface defect?

A lot of thanks,

Isabel Ruiz
- Barcelona, Spain


It sounds to me that you have "fish-eye" which is a common complaint with paints. It can be caused by numerous things, including a dirty or poorly cleaned substrate, de-wetted substrate or the cataphoretic paint is out of spec. It can also be caused by contaminating the bath with impure water; it is recommended that all make-ups should be done with de-ionisied or demineralised water I have found that cataphoretic paints and similar products have a relatively short operating shelf life. Apparently it adsorbs carbon dioxide from the air and this results in co-deposition of the gas. It is sometimes possible to dummy the gas out by depositing the paint on some scrap material. I would check your cleaners and water source. I would also examine at the metal substrate and look for any islands of either corroded metal or unusually looking metal that could cause de-wetting.

trevor crichton
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK

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

Q, A, or Comment on THIS thread SEARCH for Threads about ... My Topic Not Found: Start 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    -    ©1995-2021 finishing.com, Pine Beach, New Jersey, USA