Letter 12035

Acid copper bath testing or trouble shooting 

I have 3 / 375 gallon acid copper platting tanks. My main employee would always check and cut the tanks as needed. After 33 years he is gone. The blue stone will not elute or dissolve with heat. We are lost in how to cut these tanks. The blue stone has almost stopped the air pumps because of the build up. Can any one help with infor or were to go for charts or books how to..

Phil Johnson
- Indpls, Indiana

Phil, the concentration of "bluestone" or copper sulphate in your bath can be measured by using a Hydrometer to measure the Density. There are Tables available in most Electroplating Text books. Or you could measure the Density of the bath when it has just started to crystallize and settle on a Density slightly lower as your maximum limit. After dilution(cutting) the Density is taken and then you have a "range".

Good luck.

Patrick Wm. McILVENA
MacDermid Australia - Melbourne, Victoria, Australia

Further to Pat's suggestions, the SG tables are a combination of both the copper sulphate and sulphuric acid. When you dilute you will also be lowering the sulphuric acid which will need to be increased to the suggested level. Thus you will need to lower the SG to a level well below the saturation level particularly as you have tanks that are increasing in copper content. It is really necessary to do an analysis to know where your copper and sulphuric are either before or after dilution or you are really in the dark. What will happen with plating is that the copper will increase and the sulphuric acid decrease, so regular additions of sulphuric acid should be made and no copper sulphate.

Geoff Whitelaw
- Port Melbourne, Vic., Australia

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