Daniel

Topic: Nickel Chloride Too high

My nickel chloride is about 63 gr/lt how can i lower this value?

DustinGebhardt

Re: Nickel Chloride Too high

First, some questions to help us with your problem:

What type of bath is this? 

What is your optimal nickel chloride concentration?

What are the other bath parameters, ingredients, etc (pH, temperature)?

Are you seeing a defect from the high chloride?  If so, what is the defect?  Do you have any photos?


-Dustin Gebhardt, CEF

Advanced Manufacturing/Finishing Engineer

Moen

Sanford, NC

jimtrottier

Re: Nickel Chloride Too high

   Like Dustin said some more info would be nice.   How did it get so high?  Was it an accidental add?  Or has it been growing over time?  If it's been growing over time you need to figure out where its coming from.  Do you use sulfuric acid and not hydrochloric acid to adjust your ph on a daily bassis?  Are you dragging it in from a nickel strike?

   A quick way to lower it is to remove some of the bath and delute the main bath.  But if you don't address where it's coming from  you are going to have a lot of barrels of excess nickel sitting around as time goes on.

Jim

Daniel

Re: Nickel Chloride Too high

I saw pitting on highly finished brass parts, I  think too high chloride, not good for brass parts.

high chloride good conductivity

higher corrosive action (on zinc)

lower ductility

high stress

i believe high chloride is the guilty for some pits on brass parts but you know i cannot prove it i just guess

well i dont have pictures, because i took too many but the shiny gloss of the nickel hides the pits

my bath is a standard watts bath ph 3-4.5 temp 40°C

chloride in watts bath 40 to 60 gr/lt

Last edited by Daniel (11/14/2009 - 10:33 AM)

DustinGebhardt

Re: Nickel Chloride Too high

I'm not convinced that the  chloride is too high.  63g/L is defintely on the high end of the spectrum, but not so high as to cause pitting immediately. 


More questions for you to answer:

What is the surface tension in the bath (dynes/cm)?

Is this a rack or barrel operation?

How is your bath agitated, if at all?

Are the pits over the entire surface or only on one side?  If only on one side, does this side face up or down?

Have you tried adding more wetting agent to the bath or using a different type of wetting agent?

When you look at a pit with magnification, do you see a "fish eye", or a rise in the bottom of the pit?

Are the pits large and deep or fine and shallow?

Is this a brightened bath?

What is the thickness of the plated deposit?

What is your applied current density and plating time?

What is your pretreatment process?

Do you notice any oils on the surface of any baths, especially the nickel or the tanks leading up to the nickel?

-Dustin Gebhardt, CEF

Advanced Manufacturing/Finishing Engineer

Moen

Sanford, NC

skelton

Re: Nickel Chloride Too high

Daniel,

Lots of good input on troubleshooting your issue! I agree with both Dustin and Jim. I do not believe your chlorides are too high, however, determining the source of the higher chlorides is important. Start by eliminating any Hydrochloric Acid additions or drag-in of HCl pretreatment pickles/activators. 

I think the term, "let's go back to the drawing board" applies here. I assume you have a Hull cell? I would first see if you can duplicate this "pitting" on a brass Hull cell panel, and for the sake of testing, run a steel panel too. If "pitting" is present in the Hull cell panel, dilute the bath by 10% and run another "as-is" panel to see if "pitting is corrected. You may possibly see a slight burn in the panel if your nickel metal is low after cutting the solution, but most importantly, is the "pitting" still present?

And another easy remedy that can address your issue is adding 0.1 - 0.2% by vol Wetter. You can of course do this in a Hull cell before making an addition to your production bath. If you cannot measure dynes, you can do the old-fashion "ring test" by making a 2 - 3 inch (5 - 10cm) "ring" out of copper or steel wire. Sumbmerse this ring into you nickel solution and pull out and observe the surface tension of the "ring". If wetting agent is sufficient, tension will hold for 3 - 5 seconds or more. If ring "snaps" before you can observe the time (less than 1 second), you may consider increasing wetting agent in a Hull cell.and if proven successful, make addition to nickel solution.

And to address any organic contamination that may be contributing to this issue, make sure you have a fresh carbon pack or filter on your solution.

And last, make sure you are not plating at too high a current density. You could simply be on the borderline of burning and the increased current density is creating more hydrogen @ the surface of the part than the wetter can manage.
   
Above all, get a sample to your chemistry supplier for a second opinion and detailed analysis.

Skelton's 2-cents from his Blackberry.

Good luck!

Last edited by skelton (09/25/2009 - 12:41 AM)


Skelton, hOST
FinishingTalkLive
www.finishingtalklive.com

Daniel

Re: Nickel Chloride Too high

Hello and thanks for your help.

Let me try to show the pieces and the pits i will run a sample and try to take the advice.  This plating is done on racks, so I dont think the current density is the problem because the pits appear on the flat areas.

The brass parts are of shiny very high polished brass so high force and heat is applied to the part. I assume that it can make metallic soaps that create the problem could it be that?

Here is our process sequence….  Pretreatment - Degrease using solvent (nafta), Rinse, wash with alkaline detergent (by hand or cathodic degreaser), Rinse, Acid Dip (diluted 10% of H2SO4, or HCL), plate for 30-45-60 minutes.
This pitting is not present on our steel parts, but I will run a sample of highly polished steel to test it.  The parts have a lot of buffing compound when we receive them.

Water break test before plate: ok

Agitation :cathode movement

Here is my theory....

High mechanical force  and extreme heat cause formation of metallic soaps during buffing, lack of cleaning, chloride to high so the chloride attacks the zinc causing the material to pit.

Also some have suggested that it could be from lead smear on the  machining or dezincification due to some issue (too alkaline cleaning and high content of  zinc by the part, acid dips etc)  I discard the lead theory because I dont see lead on the machining.

I dont have a picture here so i draw the part, excuse me I’m not the best on drawing. (see below)


   BISAGRABMP.jpg
   BISAGRA.jpg

Last edited by Daniel (09/25/2009 - 03:10 AM)

DustinGebhardt

Re: Nickel Chloride Too high

Daniel,

  Thanks for the pictures, they really do help.  You are a much better artist that I am, so don't put yourself down about your drawing.

You have also given us some additional important information.  

1. The water break test after cleaning is good.  This indicates a clean surface.  I do not think you have a problem with residual metallic soaps resulting from the buffing process.

2. The pitting appears in the same place, on a flat surface.  You also suspected lead.  I feel that the lead is probably your issue.  I used to plate brass plumbing hardware that contained lead, which when machined or over-buffed, would expose the underlying lead-rich zone of the alloy.  To counteract this, I changed my acid more frequently.  I also eliminated my mineral acid in favor of an acid salt that contained fluoride (either sodium bifluoride or ammonium bifluoride).  Lead tends to passivate (oxidize) very quickly, especially after a strong cleaning cycle.  A fresh acid activator with fluoride helps condition the lead to prevent passivation until the plating can be applied.  To test this out, try to change your acid bath.  They are usually the cheapest bath to make up.  Add some fluoride if you can.  Usually 15-60g/L of ABF or SBF is sufficient.  Reduce your acid immersion time to the minimum required to activate the parts. 

2a. Sometimes, you can also identify the problem as lead contamination by wiping the parts with a very clean towel before plating.  Be sure to not get any dirt or oils on the part.

The build-up of the chlorides most likely is coming from your acid activator being dragged in to the nickel bath.  Switch to only sulfuric acid if possible.  And as Skelton and Jim have said, discontinue the use of HCl to adjust the pH of the nickel bath.  Use H2SO4 only.

3. I agree with Skelton about the wetting agent and the loop test.  When you are surrounded by good equipment, sometimes you forget about the basic tests.  Especially without air or fluid agitation, the surface tension of the bath is very important.

-Dustin Gebhardt, CEF

Advanced Manufacturing/Finishing Engineer

Moen

Sanford, NC

Daniel

Re: Nickel Chloride Too high

Thanks for your time

i must run the samples next week and then i will contact the forum again.

But by the way , why and /or where the lead could come from

Could it be that they are using brass for machining that has Pb?

Last edited by Daniel (09/26/2009 - 11:11 PM)

Daniel

Re: Nickel Chloride Too high

what about fluoboric acid, it is good? and what could be the correct amout of it for the acid dip?

DustinGebhardt

Re: Nickel Chloride Too high

Lead is often used in brass to aid in machining.  Depending upon the manufacturing process (extrusion, casting, forging, etc), the lead can cause several issues.


I'm not sure you can use fluoboric acid.  The fluoride ions may be too tightly bound to the boron to be useful.  But I could be wrong. 

-Dustin Gebhardt, CEF

Advanced Manufacturing/Finishing Engineer

Moen

Sanford, NC

GeoffPW

Re: Nickel Chloride Too high

Re plating leaded brass, fluoboric acid would be OK as the acid dip as lead fluoborate is very soluble. Suggest 5-10% by vol of 40% fluoboric acid

If the problem continues after the advice given previously by others I would try making a fresh electrolytic cleaner and try cathodic only, but I would also suggest trying finishing up with a short anodic cycle, as cathodic only can "deposit" contaminants which can lead to staining/pitting problems and a water break free test does not always show the problem. Also when checking for water break do this after the acid dip.

Daniel

Re: Nickel Chloride Too high

Thank you for all of the great advice!  I have not done the test yet but I'll let the forum know as soon as I have the results.

Last edited by Daniel (10/06/2009 - 11:08 PM)

Daniel

Re: Nickel Chloride Too high

The fluoboric acid did it well, no pits allowed to appear this time!!

But now i see small little etching maybe known as "StarDust"

Any ideas?

Thanks