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sulphate is climbing in chrome plating tank

I am having problems with the sulphate level in a 185 gallon tank. The sulphate seems to increase without any additions of sulfuric acid. It is a 100:1 bath. We have not made and add since May and the sulphate has went from 0.4 to about 0.5 oz/gal. The only thing that I am aware of the platers adding is water to maintain freeboard. IF anyone has any suggestion to offer as to why this is occurring, please feel free to share them.

Jenn Wright
- Dayton, Ohio
2002

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First of two simultaneous responses --

I understand you are talking about chrome plating. If that is so, what type of water do you use? ( city or D.I/D.M.)

Payal Mag
- Charlotte
2002

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Second of two simultaneous responses --

All chromic acid contains sulphates as an impurity! All proprietary blends which include added catalyst, ALSO contain sulphate.

At least one of the leading vendors claim their proprietary mix does not contain sulphates - it does so - and people who use it have noticed what you have noticed, i.e. creeping up sulphate. You have to compensate for it, and run a few extra analyses to keep up.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

2002

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Hello Jenn,

Is your Chromic Acid bath solution level maintain at the same level when you take sample for analysis of sulphate? How about replenishment from your chrome drag out bath? Too much replenishment from drag out may increase your sulphate and chromic acid content.

SK Cheah
- Hong Kong
2002

We use DI water on this particular tank. As for the level, the proper freeboard is maintained when samples are to be taken. Also we do add back some chrome to replenish the drag out. Thanks again for all the advice.

Jenn Wright
- Dayton Ohio
2002

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i think robert and cheah are both right 1. chromic acid contains sulphate as an impurity which leads to increase in sulphate levels also compare sulphate levels at same tank volume. use good quality chromic acid with low sulphate levels vikram

Vikram Dogra
Irusha India - Chandigarh, India
2002