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Brown substance floating in Pb-Free Tin Plating Solution

Q. Good day. I am a supplier of tin plating chemicals. One of my customers is experiencing occurrence of brown substance in tin plating solution. This brown oily substance looks like a grease floating at the top layer. Although they don't have quality issue (yet), I would like to know if anyone here has an idea about this occurrence. Thanks.
I will highly appreciate inputs.

Irene Angelie Dureza
employee - Manila, Philippines
April 4, 2016

A. Hello Irene, I would have your customer filter a small amount of solution through filter paper in the lab. You can get a better look at the substance then. Does the tank have any hoists above it that could be leaking grease or oil? There is also a tin bath additive that could have been added in excess. I would "skim filter" the surface of the solution, analyize for the additive, change filter tubes, and see if the problem re-occurs. Filter tubes should be leached with hot DI water, or 10% sulfuric acid (only if the bath is a acid tin sulphate bath). Also rule out any cause of grease getting into solution.

Mark Baker
Process Engineering - Phoenix, Arizona USA
April 7, 2016

A. Good day Irene.

I must agree with the comments from Mark regarding oil/grease.
Could this be a tin/lead bath? I have also seen this brown floating substance in my baths, but they were quite "aged" and were subject to high volumes of barrel production. Check the the condition of the anode/bag material, as the tin/lead anodes do produce some brown"sludges". I found this brown substance in our tin/lead barrel process, and a leaking grease/oil nipple on the barrel drive shaft was the cause.

Regards,

Eric Bogner, Lab. Tech
Aerotek Mfg. Ltd. - Whitby, Ontario, Canada
April 9, 2016

A. Hi Irene
If your mystery substance was grease you would be seeing severe adhesion and other problems.
My guess is that someone has heavily overdosed with brightener or some other additive.
I would remove the floating material by laying a sheet of absorbent paper (newspaper) on the surface and investigate the amount of additives being used

Geoff Smith
Hampshire, England
April 9, 2016

A. I had similar issues in my continuous plating tin and tin/lead tanks. We utilized skimmers to remove the substance and then changed the antioxidant we were using. This completely solved the issue. I would speak with your supplier to see what options you might have. If you are making your own I would start with that.

Ron Hupe
- Beaumont, California, USA
April 12, 2016

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