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topic 11706

Problems with Bright Nickel Plating Baths




Stardusting

 

Q. Hello and thanks in advance for the help , we do mostly show quality plating for cars, motorcycles, etc. All of our nickel and chrome plating is plated over acid copper which has been buffed to a mirror finish. Because of this mirror finish, imperfections are easily seen and one that we have from time to time is a "stardust" or white speckles that show up in the nickel . These small speckles show up over the whole part except for the bottom side -- it's almost as if a white dust settles on the part during the nickel plating and we are having a hard time trying to figure out the cause and how to prevent it. Thanks for the help.

Billy Brown
- Lyman, South Carolina


 

A. Billy:

This question about stardusting was asked in our forum and a electroplating chemist answered it. Here is his answer.

His problem, if he is using brighteners, could be:

1) excess brightener
2) insufficient leveler
3) insufficient carrier
4) pH too high
5) insufficient air agitation

Hope this helps!

Tom Haltmeyer
- Peoria, Arizona


 

A. Stardusting is sometimes caused by precipitation of calcium or magnesium salts in nickel plating solutions. Check to see if hard water is used to make up evaporation losses. The fact that it settles on shelf areas indicates that this could be the problem.

tom pullizzi portrait
Tom Pullizzi
Falls Township, Pennsylvania


 

A. Make sure that your boric acid content is not supersaturated. You probably have boric crystals that are settling in your parts. A quick way to check is to take a sample of the bath in a beaker and let it cool to room temperature and if you see crystals forming fast like an hour or two then the boric is to high. To remove it simply cool your entire bath for several days with no agitation and simply scoop the boric acid from the tank bottom.

Russell Richter
- Danbury, Connecticut, USA


 

A. It is important to know how you are re-activating the copper before nickel plating. If your supplier does not find anything wrong with the nickel bath per se, it is probably in the activation/cleaning of the buffed copper. Also, this type of problem sometimes can occur due to high organics in the copper bath. A carbon treatment of the copper could solve this problem.

Gene Packman
process supplier - Great Neck, New York


 

A. The fact that it is only on the top surfaces would indicate it is insolubles in the nickel tank. When the trouble occurs, take a liter and filter through a buchner filter funnel, rinse and examine the filter paper under low magnification. If iron contamination then will be brown ppt, if calcium whitish, black nickel sulphide etc. Check anode bags. Do similar check on outlet of filter to ensure there is nothing passing filter. Check air source for particulate contamination.

To check if the problem is coming from a source before the nickel, wipe one piece on a top significant surface just prior to going into the nickel and see if any difference between this and the part next to it

Geoffrey Whitelaw
Geoffrey Whitelaw
- Port Melbourne, Australia


 

A. If you feel any roughness in the areas of a "stardust" more likely you are dealing with the solids: check your bags, filtration, PH, concentration of boric acid, temperature, condition of your racks(to eliminate contamination from previous operations), conditions of your air source, especially presence of oils and solids in the air. Also it's highly recommended to make the Hull cell test to see the area of C.D. where the problem appeals. If it's on a high C.D. area repeatably, then consider a possibility of high level of organic contaminations as well and full bath chemical treatment ( 35% Hydrogen Peroxide [linked by editor to product info at Amazon], 5.5 pH, carbon)would be necessary to perform. Also pay attention on the carbon dust like a source of organics and roughness from solids, so make sure the mesh of your filter cartridge is correct to halt any solids (I'm using 1 mkm).

Vlad Neyshtadt
- Fountain Valley, California


 

A. First I would recommend to improve filtration. If the problem is mainly on the "shelves" it is probably a result of poor filtration. The second parameter is the quality of the water used in the plating solution and in the rinses.

sara michaeli
sara michaeli signature 
Sara Michaeli
chemical process supplier
Tel-Aviv, Israel




Bright Nickel Plating Turns Gray the Next Day

May 19, 2014

Q. Hello Everyone, this is my first post here and I really hope you guys can help me.

I have a problem with the bright nickel deposition, you can see the picture here:

11706

What do you think it is?

Enrique Guillen
- Guatemala


May 2014

A. Hi Enrique. The picture probably helps to confirm the problem you have in mind, but what you are finding unsatisfactory is not as obvious as you might think :-)

Are you the customer or are you from the plating shop? How big is the part, maybe 1" x 2"? What is it made of, cast brass? It's hard to judge/guess what you consider bad about this part based only on a low resolution photo --
1. There are several scratches.
2. There looks to be a grainy unpolished area near the lower right.
3. There may be blistering but I can't tell.
4. Photos can be deceiving but it looks like the part wants quite a bit more vibratory finishing before plating.

Tell us more.

Regards,

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


May 23, 2014

Q. Hello Ted, thanks for your reply

This is a zinc piece, about 1 inch tall, we hand polished it very nicely.
Cleaned it, alkaline copper and acid copper, everything looked great at that point, so we applied nickel to the piece and it looked good, but in the center of the piece, there were some steps, like the nickel was not deposited well on those parts. They were close to the wire and most of them have the problem in the back side of the piece, where it had little contact with the wire, but some looked bad on the front too.
After a day the piece started to look gray on those parts.

Thank you for your help!

Enrique Guillen [returning]
- Guatemala


May 2014

A. Hi Enrique. If the volume supports it, the parts ought to be plated on proper plating racks rather than simply wired. The best bright nickel plating requires a current of about 40 amps per square foot, and it can be difficult to get consistent bright nickel on parts that are flopping around on wire such that the current density varies; and small gauge wire may be limiting it as well.

I don't have enough experience to guess why the parts are discoloring a day later unless the nickel plating is just very thin in those areas for the reasons I mentioned. Good luck.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


May 29, 2014

A. Good day Enrique.

It might be a number of conditions which are responsible for the nickel plating darkness/thin deposit which turns grey.
Firstly, check for metallics, as they show up in the LCD area.
A quick fix/check would be to dummy plate at LCD 2-5 ASF overnight. Copper can cause LCD darkness.
Check bath concentrations and pH, making sure they are in operating parameters.
Excess brightener/insufficient carrier also causes poor/dark LCD coverage.
Organics can also cause dark LCD. Try carbon on your filters, but remember carbon removes brightener and wetting agent.
Try a hull cell panel to determine the solution after trying the above possibilities.

Hope this was helpful.

Regards,

Eric Bogner
Aerotek Mfg. Ltd. - Whitby, Ontario, Canada



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