Pitting problem in bright nickel plating bath

A. Hi Ibrahim,

The first step is to determine whether the pitting is gas pits / hydrogen pits.Without air agitation, the mechanical agitation needs to be very good! My wild guess is that the top of the rack gets pretty good mechanical agitation whereas the bottom sort of pivots around a stationary point and receives inadequate agitation to dislodge the hydrogen bubbles.

In addition, unless the anodes are significantly shorter than the racks, the current density is probably higher on the parts at the bottom of the rack, generating more hydrogen. Please measure the thickness of the plating on a part at the top or the rack and a part at the bottom of the rack and see if it confirms the higher current density on the parts at the bottom.

Luck & Regards,


Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Need quick confidential answers? $25
Need project assistance? $100/hr.

A. Water break test, after clean the parts cleaners then rinse follow by acid dip then rinse.
take the part out after acid rinse then grab white tissue paper wipe the part if you see black residue (smudge) on papers means cleaning problem
sometime see part after acid dip oil pattern on part.

A. Hi !

If you have pitting problem in your nickel tank, can be several reasons.

1. Check overhead structure on your nickel tank for leaking oil or grease.

2. May be you have compressor air in your nickel tank drawing oil into your tank continuously, would not completely help anti-pit chemical add.you need air blower instead of compressor air.

3. Check your nickel strike or copper strike before bright nickel tank any oil floating.

4. May be your parts are pitted before you plate or Electrocleaner rectifier adjusted too much current for those parts.

5. Check cleaning for those parts for water break test.

Dear Popat,

Thank you very much for your response. Could you please give me information about this water break test?

Sevim Topaloglu
- Izmir, Turkey

A. Hi, Sevim. There are ASTM specifications for water-break tests, but what most platers mean by this phrase is that when a part is removed from the rinse after the cleaner tank and the rinse after the acid dip tank, the water must form a perfect sheet on the surface; there must be no breaks or dry areas as this indicates that the parts are not truly clean.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Need quick confidential answers? $25
Need project assistance? $100/hr.

A. Mr Patel's advice is sound, however I would like to add some thoughts. Look at the pits. Are they like small explosions (gas pitting) do they have a tail (oil/grease?) or do they have regular edges (particulates). Is the pitting more pronounced in any one current density area (burning?, excess gassing) or more prevalent on flats (shelf roughness/particulates). Is your water supply "hard" (high in minerals) if so could be from calcium particulates which redissolve when bath is cooled.

Finally, are you by any chance plating on leaded brass? This would necessitate a special cleaning process.

A. Where do you have the pitting, is it all over the parts or only on the shelf ? If it is on the shelf, it means that you have to filter the solution. I assume that you use continuous filtration! The anode bags ⇦ huh? must be higher than the solution level. Lack of anti pitting is indicated by pits on the high current densities not all over the parts. As for water, you must use d.i.water for the plating solution.

A. Pitting may also occur due to lack of wetting agent.

A. When operating a nickel plating bath you must constantly use a carbon packed filter to prevent the pits. Pits can come from many different sources, you will have to investigate and see if and where you are introducing "contaminants" into the bath.

A. Hi Sevim Topaloglu,

As you are using brass parts for plating,your bath could have copper and zinc contamination. You will have to remove the contamination first to get pit free deposit.

A. Clean the filter and put a new fresh carbon pack in it and filter overnight before attempting to plate, also if you are using air agitation be sure the air is coming from a clean source and not contaminated with any lubricant.

A. Hey Mike,

Never had that happen before so my advice may not be very good, but I do plate a lot of nickel. Algae can be unicellular to visible in size. My nickel filters with a good carbon/filter-aid pack gets out stuff down to about 5 microns. Unfortunately some algae is smaller than that. If it was me I'd try a full scale batch hydrogen peroxide/carbon treatment in a separate tank, with all the solution being transferred by filter. Ask your brightener supplier for their specific procedure. The peroxide does a dandy fine job breaking down many of the organics in a bath. It might do a number on the algae. (Oh yeah, rotate your brightener stock. The stuff has got a shelf life.)

A. MIKE !

You have a pitting problem in your nickel bath, I would like to do, make small quantity fresh nickel solution then run the panel then see any pitting.

Clean your hull cell and hull cell nickel anode then run the panel from your tank solution , see any pitting.

Some time hard to catch the pitting on the hull cell panel.

Do you have rinse after nickel strike ?if yes you have to clean the wall with small amount of nickel wetter mix with water then wash wall using water then refill tank with water and adjust pH between 4 and 5. if you have liner in rinse tank then easy to clean after that run the production. let me know still you have a same pitting problem or not.some time incoming water rusty from pipe create pitting problem. Do you have filter in rinse tank?

Check your nickel bath surface tension , Make sure between 40-45

A. I am in the nickel plating business for many years and never heard of algae problems in these solutions. In EN solutions, gold plating solutions etc but not in electroplating nickel solutions. By the way, most nickel plating brighteners contain a small amount of chemical that kills algae.

Somehow I am not sure that you tracked down the problem in the right way. Addition of brighteners to a hull cell will always increases pitting as pitting is more significant on a bright panel.

How about filtering? Did you try to filter the solution before the hull cell test with a 1 micron filter? Take a good look at the filter paper after filtering 1 liter of solution on a 1 micron filter paper. Did you check for chromium contamination? A few ppm of hexavalent chromium can cause an overall pitting.

A. Generally, the rule of thumb for nickel brightener is 12 to 18 mos from date of manufacture. I have not seen the pitting problem you describe happening from algae. If you have this problem the brightener would have organic material floating in it. The advise that was previously given is correct, but before I went through the treatment process I would try, in a hull cell, adding peroxide (33%) at a rate equiv. to 2 qts/100 gallons of bath solution, keep heated and agitated for thirty minutes before running after panel. Then add up to a full charge of wetter and check results. You also might be able to get away with a heavy carbon pack and additional wetter. This presumes that what you have is not a breakdown of organic brightener or a polymerization product of same. If this were the case, probably the batch treatment would be the correct direction.

A. Since you have identified the brightener to be the problem, raise the issue with your supplier. I am sure they will be more than happy to solve the problem as it is in their commercial interest.

A. Mike,

I used to run it to that occasionally when I ran bright nickel. If you think it's the brightener, take a gallon of the old solution, add 500 g of granular carbon and 50 ml or so of H2O2. Heat it up to 150 for a while and filter really well. Do a hull cell and see if it's dull all the way across. Then put new brighteners and wetters in and try another one. Make your supplier do a lot of this leg work if you don't have the time. A good practice I used to do was add .05% H2O2 just before dummying overnight each week and run a clean carbon pack all the time.

A. I HAVE A 1000 GAL NICKEL TANK AND I HAVE SEEN THIS PROBLEM BEFORE.

PITTING IN THE NICKEL IS MOST OFTEN A PH PROBLEM AND NOT A CONTAMINANT. WE KEEP OUR BATH AT 4.3 AT ALL TIMES. KEEP IN MIND IF YOU USE THE PAPER TEST STRIPS THEY GO BAD FAST AND GIVE FALSE READINGS. AN ALGAE PROBLEM IS POSSIBLE IF YOU USE A NICKEL RECOVERY TANK AND PUMP IT BACK INTO THE NICKEL TANK WITHOUT A FILTER. THE PITS FROM THIS USUALLY LOOK GRAINY OR GIVE A SLIGHTLY SAND BLASTED FINISH. IF THE PITS ARE LARGE IT IS PROBABLY NOT ALGAE. IF YOUR TANK IS AIR AGITATED, CHECK THE PIPING TO MAKE SURE THAT THEY HAVE NOT RISEN IN THE TANK. AIR WETTER SPECIAL ALONG WITH CARBON FILTERS SHOULD TAKE CARE OF THE PROBLEM. IF NOT A SHEET METAL PANEL WORKS WELL FOR A DUMMY.

A. I know what you talk about . just do filtration using 1 micron filter paper

A. Hello, Lloyd. This letter that you have posted against includes a nickel plating formulation and some notes about some typical problems and how to address them. But, as you can see, even the parameters for operation of the nickel bath alone -- let alone all the pretreatment steps -- is a very broad topic for an internet posting. Please see our list of "must have books" (I would especially recommend ASM Handbook volume 5, Surface Engineering ⇨
as it will give you an introduction to the necessary brighteners, carriers, and wetting agents). Then get back to us with your more specific questions. Thanks!

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Hi, Sieglend. Considering what you have told us, and assuming that you have reviewed the previous responses to this thread without solving the problem, my feeling is that the "stamping process" is embedding oil into the cover that your cleaning process is not able to remove.

Please pull a number of these logo cover plates and scrub them well with powdered pumice ⇦ on eBay or Amazon [affil link] and a tampico brush before racking them for your regular pretreatment and plating, and tell us the result. If the problem goes away on the hand-cleaned parts, you know that you need to improve your cleaning process to deal with the problem. Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Dear...
Everyone faces this problem so you should follow the steps:
1- you should make chemical analysis to know the concentration of Boric (Boric decrease = pitting)
2- measure pH (should be from 3.5 to 4.5) and the ideal is 4.2 (more acidic = pitting)
3- use DI water
4- make sure about type of anti pitting agent (powder for Trembling [mechanically agitated] bath) (Liquid for blower bath)
5- perfect clean for surfaces
6- anodes bags level must be higher than solution level and must be cleaned in hot water before use if it made from cotton
7- Continual filtration must used.

A. How pitting made?

"During the electrolysis of a water base plating solution, hydrogen is evolved at the cathode surface. Very minute bubbles that form should get quickly detached and escape from the cathode surface towards the open surface of the solution. At a spot, where the bubble has lingered, deposition is reduced and a pit is left."

In addition to above comments,
if pitting is with foggy deposit then possibility of chromium will be a cause.

A. PLEASE ALSO CHECK CURRENT DENSITY
NICKEL ANODE
SEMI BRIGHT NICKEL TANK
NICKEL CHLORIDE CONCENTRATION

A. More current more tiny bubbles, more bubbles more tendency to hydrogen cling on surface.

It is just the first thing I have in mind, check wetter.

• Topic #443/80 "Gas pits in nickel plating"