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Improving throwing power of tin bath

I need to increase the throwing power in an acidic tin process. I use the traditional formulation but my problem is to plate inside a tube with 2 inches in diameter without auxiliary anodes that means I need better throwing power. I am not sure if an alkali formulation should be a good aim.

Thanks in advance.

Jose Cesta
Servico Nacional de Aprendizado Industrial - Sao Bernardo do Campo, Sao Paulo, Brasil
 

What type of acid tin are you using? We have fluoborate, MSA and sulphate tin processes in our shop, and I find that the sulphate tin has the best throw of all. In fact, with only one anode in the bath, it will throw behind a flat part, coating both sides. Hull cell panels of these baths are coated front and back.

Michael Brewington
plating shop - Salisbury, Maryland, USA
 

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Usually alkaline processes have better throwing power than the corresponding acid process. Alkaline tin has comparable throwing power to cyanide copper.

George Shahin
Atotech - Rock Hill, South Carolina
 

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HAVE A GOOD DAY.

The problem is as follows: I need to plate tin inside a tube 5 inches long and 2 inches in diameter. I can not aplly auxiliary anodes because I intend to use a automatic line. The only way is to use a tin bath with the best throwing power. My sulphate tin process with nominal strenght do not work well regarding my needs because I have only a few tin in microns in the inside of the tube. Maybe somebody know a good literature about new developments in tin bath?

Thanks in advance,

Jose Francisco Cesta
SENAI - Sao Paulo

You could use non-conductive shielding on the racks to improve throw inside the tubes. If the tubes' ends are facing the anodes, fixture a plastic panel near the end of the tube. The panel could have a hole cut in it that's smaller than the ID of the tube.

Michael Brewington
plating shop - Salisbury, Maryland, USA