Electroless Nickel Plating of Brass: Q&A, Problems & Solutions

A. No, but copper alloys require catalytic activation in EN bath. Otherwise, maybe, because you may see some immersion plating.

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.

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 worse, 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.

A.
- add some aluminum or iron wires
- catalyze with a solution of palladium chloride
- electrochemical nickel strike (Watts or Wood's nickel)

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 adhesion than what you are actually doing now. Adhesion problem does crop up once in a while, though.

Good Luck!

A. 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 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 phosphorous baths (check with your vendor for specific values).

Hope this helps!

A. Hardening electroless nickel coatings will severely reduce their corrosion resistance and may cause the coating to crack. However, it will improve adhesion.
Ron Duncan [deceased]
- LaVergne, Tennessee
It is our sad duty to note Ron's passing on Dec. 15, 2006. A brief obituary opens Episode 13 of our Podcast.

A. Regular cleaning cycle used for plating on zinc or brass. Then, a strike of a high pH EN, then regular high phosphorous EN.

A. Or alternatively, you can use a copper cyanide strike prior to the high phosphorous EN.

A. You need to chemical polish the brass first.
- give a quick copper flash
- quick layer of watts nickel
- then into ENP

A. To be on the safe side, you need a nickel strike prior to the EN.

A. The following is opinion only!
I would start by looking for a harder brass alloy.

EN is quite controllable by a good operator with good equipment and a good solution. Completely uniform plating above 0.0015 gets to be tricky as well as expensive, so I would start with that and see how well it works.
Your external threads will have to be cut undersize to accommodate the thickness on each side of the same thread. It will help if you truncate the thread a little more-say 75% vs. an 80% thread. You probably can avoid masking, but masking does not have to be expensive.

A. Too many questions for a free ride Matthew, don't you think? But there go my two cents.
Chrome is harder and easier to adhere to brass than any EN but it's not uniform specially on threads. Three tenths is tight but feasible for EN. Now, how much wear can the mechanism tolerate before being non-useful? You said you are used to plating less than 1 mil and there must be a reason. There is no need to specify 3 or more mils if 1 or 2 mils will scrap the part.

A. Your proposed thickness of 0.0010 - 0.0013 inch should be adequate. The EN will either be successful or not in this application. If it is not successful, a higher thickness will not help.

EN with 4% Phosphorousl is slightly harder and more wear resistant than lower (or higher) phosphorus contents and would be best for your application.

Alloy C36000 contains 3% lead, which can create an adhesion problem. EN will stick to it, but only if the lead is completely removed. Plating threads increases their pitch diameter by four times the thickness of the coating.

A. Hi Karthikeyan. First step is you need to buy a copy of ASTM B733 if you don't have one; it's internationally copyrighted, and you can't specify it or certify compliance with it unless you have a copy.

Although I doubt that anyone (except a plating consultant you retain) can provide you with the right and full cycle of treatment for your situation, there's an awful lot on information on this page which people will probably be happy to clarify for you. Some things you'll need to determine are why you are applying electroless nickel, because that will help determine whether you need high, low, or mid phosphorous, and whether it needs heat treatment. You'll also have to think about this issue of reliably "jump starting" the plating, and whether an electrolytic nickel strike should precede the EN process, and as Ron Duncan warned us, what you are going to do about the lead in the C36000. Best of luck.

Regards,