Letter 29015

Density of chemical bath changes [India] 

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I Electropolish Steel My Chemical Bath has a composition phosphoric acid : sulphuric acid: water in the ratio 6:3:1 They are all commercially pure acids The tank capacity for elctropolishing is 600 lt or 150 gallons Temperature 60-80 degrees C , 10volts, 400-420 Amps The Component being Electropolished is 3 sq inches I get a very good shine but after a month the density drops and amperage falls to 9 volts for the full capacity of the rectifier and the shine becomes very bad.

The reason that this happens is because when steel gets electropolished iron is released in form of phosphates , sulphates and some free irons and nickel, which take a very long time to settle, and this is the reason the current does not flow.

Is there any additive that can be added to remove the iron so that current can pass through and we do not have to throw away this bath solution every 20 days. Or there should be some way how the sludge can settle quicker. Any Help would be appreciated.

Thanks,

Rajiv Jain
Electropolishing - Aurangabad, Maharashtra, India

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