Electroless Nickel Plating of Brass
Q. 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 Wood's 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 heat treat of say 450 °F improve adherence and ductility?
I Thank you and look forward to your comments.Robert Sachs
- Ontario, Canada
A. 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 (0.5 mm to 1.0 mm) x 10 to 20 mm 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. Adhesion problem does crop up once in a while, though.
Good Luck!Cheah Sin Kooi
. - Hong Kong
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 Wood's 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
Q. Can brass be electroless nickel plated by adding a small quantity of steel to start by galvanic. Or is DC current required, and what voltage or amperage, parts negative? Surface preparation is simply alkaline followed by acid cleaning sufficient or can a low % sulphuric acid be used. What is the best method?Robert Sachs [returning]
- Morrisburg, Ontario, Canada
- add some aluminum or iron wires
- catalyze with a solution of palladium chloride
- electrochemical nickel strike, (Watts or Wood's nickel)
Falls Township, Pennsylvania
Q. Electroless nickel plating brass? Will this contaminate the electroless nickel plating bath normally used for steel?Robert Sachs [returning]
- Morrisburg, Ont, CANADA
A. No, but copper alloys require catalytic activation in EN. Otherwise, maybe, because you may see some immersion plating.Mary Ross
- Oklahoma City, Oklahoma
A. Copper is not catalytic in electroless nickel so it needs 'jump starting'.
Our normal method is we have an old steel anode cage (the expanded metal give high surface to volume ratio) we put in the tank first and hold the parts against to get them plating (strange this but you only have to do one wire on a bar and all the parts go).
Other methods - nickel strike in electrolytic bath like stainless steels are treated.
Use electricity like a normal plating bath to jump start the work.
surface treatment shop - Stroud, Glos, England
A. Dear Robert:
If you process a large volume of parts and some of them do not start right away by any of the mentioned methods, or worst, if some parts happen to drop inadvertently in the bath (which is not unusual for large volume operations) the electroless chemistry will dissolve bronze and get contaminated. Then I would recommend another bath for these parts.Guillermo Marrufo
Monterrey, NL, Mexico