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Nickel Plating Brass
I am attempting to electroless nickel plate low lead content Brass. The parts are small pins. The electroless nickel is a mid phos.
I have had some success to date with alkaline cleaning, followed by acid clean then plating with a small quantity of steel to initiate plating. The problem is to get good plating adherence to the brass and to be ductile enough to withstand crimping of the part following plating. Would better adhesion be acquired with the use of DC current at the electroless plating to initiate the plating?
Is there a specific process that can help?
Can a woods nickel strike be used prior to electroless nickel and will this give better adhesion and ductility?
If the brass is nickel plated will a low temperature heattreat of say 450F improved adherence and ductility.
I Thank you and look forward to your comments.
Robert Sachs- Ontario, Canada
Mr.Robert Sachs,
To answer part of your question, may I suggest Wood's Nickel strike followed by Electroless Nickel. I have seen it done on small diameter brass tubes (0.5mm to 1.0mm) x 10 to 20mm length used in the manufacture of contact probes. The parts go through some crimping process on the tubes and may exhibit much better adherence than what you are actually doing now. Adherence problem does crop up once in a while, though.
Good Luck!
Cheah Sin Kooi. - Hong Kong
Robert:
Lead, even in very small amounts, will have a detrimental impact on the adhesion of the electroless nickel to the brass. A nickel strike is strongly recommended prior to EN plate. Use of a nickel strike would also eliminate the need to use current or other methods to initiate the EN plate. Sulfamate is preferred because it is usually more ductile and is more compatible with EN baths, but watts or woods will also work. Also, avoid sulfuric acid and high current anodic electrocleaning in the pre-plate cycle.
If your pretreatment is adequate and you still experience adhesion issues during the crimping operation, you may want to try running your EN bath at a lower pH to maximize the %P in the deposit. Generally speaking high phosphorous EN deposits are a bit more ductile than those from mid phos baths (check with your vendor for specific values).
Hope this helps!
Mike Barnstead- Waterbury, Connecticut