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Ted Mooney, P.E. RET
Pine Beach, NJ
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for Metal Finishing since 1989
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Bleed out on brass plated cast steel after clear lacquer dries
Q. Hello, I need help! I have bleed out on my brass plated cast steel, it usually occurs a day after it is sprayed. I've tried many lacquers and still am having bleed out. My process for plating is Prepped and cleaned surface, copper strike then to the copper cyanide bath , usually with cast steel I will let hang in the copper bath 1 to 1 1/2 hours
before I plate in the decorative brass cyanide, My pieces I am plating are 100 year old or better. I have also tried baking in the oven the parts after finial plate it helps some but still noticeable. I was told that I might want to try a water based clear lacquer. At this point I am open for suggestions and a possible cure for my problem.
can someone help me?
plating shop owner - Abbottstown, Pennsylvania
September 9, 2009
A. Hi, John. "Cyanide bleed out" is an age-old problem in brass plating. You may find some info via the search engine, but a literature search may be more fruitful. The basic problem is that you need to improve your rinsing, even if it isn't easy. Alternate hot and cold rinsing may be of some help.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
September 10, 2009
A. Been there done that. At the end of the line rinse hot/cold/hot/cold/hot/cold. Do not lacquer. Hang up for one week and let it spot out, buff or scratch brush off the bleed, THEN lacquer.
Robert H Probert
Robert H Probert Technical Services
Garner, North Carolina
September 11, 2009
May 20, 2013
Q. Hello,
Medals and sports gifts are our main core business. In the past, we used zamak for our castings. But recently, due to a fierce market we had to sail through other venues in order to offer a more competitive price. Hence, now, we are more competitive by using lead castings for our medals.
I have also switched from flash gold to flash Brass on Nickel for gold finish medals.
My sequence is as follows:
1. Hotsoak clean
2. Alkaline Copper
3. Acid Copper
4. Bright Nickel
5. Flash Brass
6. Chromate passivation
7. Water based lacquer
After 3-5 days, staining and discoloration appear and this is my major concern.
If it is bleeding of cyanides after plating, please advice how to tackle this problem.
And also, any piece of information I should be aware of regarding difficulties using lead as my base metal.
Thank you.
Laboratory technician - Port-Louis, Mauritius
A. Hi cousin Rhiaz. Switching to lead is a mistake regardless of fierce markets, especially if there is any chance a child could get hold of the medal; it is likely that some countries have banned the product. If these medals are worn, the chromating is a mistake as well; it is a carcinogen. Water based lacquer is, in my limited experience, a third mistake, not being as robust as NC lacquers or any of a number of alternative clearcoats. I don't want to be rude, cousin, but I'd prefer to not wear a brass plated and chromated lead medal :-)
I think you would be better off stopping after nickel plating, and either sending the medals out for PVD deposition of titanium nitride, or applying a gold-toned electrophoretic lacquer to the nickel. But we appended your inquiry to a thread where Robert Probert suggests a cure for the cyanide staining if you wish to continue that way. Best of luck.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
May , 2013
A. Ted's advice is what you need to do. Meanwhile, note that when you mix alkali and acid in the pores of castings you invite bleed out with temperature and humidity changes, so let's stay all acid. Eliminate the alkaline copper, and change the "acid" sulphate copper which forms insoluble sulphate compounds with lead, and change to fluoborate copper which works much better on lead and lead alloys.
Robert H Probert
Robert H Probert Technical Services
Garner, North Carolina
May 24, 2013
May 28, 2013
Q. Dear Ted,
Thank you for your valuable response :-). And your advice has been well taken on board. I do realise that switching to lead and water-based lacquer is a mistake :-(
I am working on switching back to zinc diecast.
As you suggested, electrophoretic could well be an alternative and it seems to have a nice, bright finish as well.
NB: Am glad to be part of the family, cousin :-)
@ Robert Probert:
Very often I get bubbles formation after nickel, and upon examination, base metal appear instead of copper layer.
I have done my homework on how to successfully plate on lead and even had long chats with my supplier but!!
Your explanations on lead is clear, chemically precise and useful.
If I need to plate using lead castings:
What are the, in your opinion, proper line sequence to finish on bright nickel including chemistry and different choice of acid dip in the prep line?
Is there any specific choice of grade for lead to use in plating, or I mean, can presence of impurities prove to be a headache?!!
And secondly, when plating using zamak, can I use the same line as for lead?
Regards
- Port-Louis, Mauritius
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