Home /
Search 🔍
the Site

Chime right in! (no registration req'd)


"Hard coat coil problem"


Please, help!

We have hard coat anodizing tank. H2SO4 conc. 300 g/l. Max rectifier capacity 2000 amp. T = 32 F. We were using 316 SS platecoil as a cathode (and cooling coil) for 10 years. We had to buy a new one 10 month ago. It started to etch recently. What is causing the problem? (Current? Acid?) We know that Zr is the best choice, but we would like to know what is the " best buy". Is it possible to use SS as a cooling coil & use some other material as a cathode (ex. 6063 AL)?

Thank you,

Marina Metter
- Baltimore, Maryland


300 gm/L is too high, causes very soft coating and/or rub-off. Get down to 165 gm/L or if copper alloy in the 2000 series use 200 or 225 gm/L. Stainless Steel is theoretically OK, however, in the presence of any galvanic relationships it will dissolve, find the galvanic voltage and reverse it with a small battery charger. You waste heat and power using stainless steel cathodes - instead the current standard is Aluminum alloy 6063 T5 or T6. There is controversy as to whether to weld or bolt. People who sell ready to use aluminum cathodes recommend bolting (easier to ship). I am still old fashioned and prefer welding.

robert probert
Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina

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