Metal finishing Q&As since 1989

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What happens if chrome lead anodes are too long?

Sir,
I have a part to hard chrome and the dimension are 30 mm in diameter X 50 mm in length.The parts are placed in a hard chrome solution with the lead anode of 700 mm in length. My question is what happens to the anodes that is way below the part which are not plating anything? Does the anodes takes in more amps with a long anode than a shorter anode?

Thank you
Regards,
JT

James Tessensohn
Plater - Singapore
2005

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Although it may be impractical to change the anodes for each different part, it is not really right for the anodes to be longer than the part because that accentuates rather than minimizes build up on the corners; rather, they should ideally be shorter. The bottom of the anodes will not draw much current but they will draw some.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2005

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First of two simultaneous responses --

The same thing as Ted said with a different spin. Depending on the depth of the tank you will get a very significant amout more plate on the bottom and lower corner as well as more on the top and top corner. Commonly referred to as a dogbone effect. If you are only putting on a thin layer of chrome, it will not be too bad. If you are putting on 0.003" per side, you will have a huge amount of grinding to do.
If you are doing a lot of these, it would be cost effective to use conforming anodes. They can be tweaked to have very little chrome go where you do not want it and it will plate3 to 5 times faster than tank anode on this type of part.

James Watts
- Navarre, Florida
2005

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Second of two simultaneous responses --

If build up is a problem then you could drop in a plastic shield in front of the lower part of the anode to prevent current from that area.
May need to dummy the anodes to reactivate if a chromate film passivates the bottom

Geoffrey Whitelaw
- Port Melbourne, Australia
2005