Sudden high conductivity in Phosphoric acid anodizing bath


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January 18, 2011 I have a 1400 gallon tank used for phosphoric anodizing.
Just overnight the bath became highly conductive and is causing aluminum parts to etch similar to running the rectifier in reverse.
What could have caused a contamination to the bath? Ron Tautic
Employee -Suffield, Connecticut, USAJanuary 19, 2011Hi, Ron. I'd suspect the rectifier before the plating bath. Are you verifying the conductivity in some independent way? Regards, Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
January 20, 2011

It sounds like someone added some hydrochloric acid to your anodize tank. Check it for chlorides. Unfortunately, there is no cure for this problem .

Lyle Kirman

Lyle Kirman
consultant - Cleveland, Ohio
January 20, 2011

It's definitely the bath.
We took approx. 5 gallons and ran it in a small test tank with a portable rectifier and it acted the same as the 1400 gallon tank.
Extremely high amps.

We ended up removing the phosphoric acid, rinse out the large tank and refilled with new chemistry.

The systems now operates correctly.

Prior to experiencing the high conductivity the tank was previously used with Sulphuric acid for approx. 8 months

I suspect that some sulphuric was trapped behind the lead and mixed with the phos..
Are the two compatible?

Ron Tautic
-Connecticut, USA

Disclaimer: It is not possible to 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; some names may be fictitious and some recommendations may be deliberately harmful.

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