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removal of electroplated Nickel from steel or bronze

03/29/2008 6:02 PM

I have a need to remove a deposited nickel (or any other metallic) layer

thickness is 3 to 30µm

without any disturbing actions on the high precision surface below the coating.

Does anybody know:

How to remove?

Which bath, etchant .. used?

How to prevent attack of the surface beneath?

Thank you

RHABE

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#1

Re: removal of electroplated Nickel from steel or bronze

03/29/2008 8:10 PM

'without any disturbing actions on the high precision surface below the coating.'

Please describe precision surface and condition, material specs, etc..

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#2
In reply to #1

Re: removal of electroplated Nickel from steel or bronze

03/30/2008 1:06 AM

Repeating bwire's questions... plus (or any other metallic)??

Nickel can be removed using mild hydrochloric acid (Muriatic Acid is 28%HCl).

It will not remove all metals or leave certain high precision surfaces untouched.

It is also quite bad on Aluminum, so it may deteriorate your bronze depending on its Al content. It is OK for steel but test on scrap parts...

You should passivate your surface afterwards using a sodium bicarbonate solution+PH indicator if you plan to reuse the solution.

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#3

Re: removal of electroplated Nickel from steel or bronze

03/30/2008 2:34 PM

The procedure you need is reverse electro plating.

I have just done all my engine cases as they were chromed. The lustre chrome is deposited on a copper layer which is also electro plated.

As the engine cases have journals in them and they are made from an aluminium alloy, I decided to have them done professionally by electro plating specialists.

Don't go and be a hero with acids, you will end up ruining your parts.

Contact a local electro plating company for advise and see what they can do about it for you.

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#5
In reply to #3

Re: removal of electroplated Nickel from steel or bronze

03/30/2008 4:52 PM

Hi,

I did a trial with a renowned electroplater but the result was catastrophic.

RHABE

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#6
In reply to #5

Re: removal of electroplated Nickel from steel or bronze

03/30/2008 5:27 PM

What happened?

I did mine and apart from the time they took it was done fine. One of the bushings has damaged as I forgot to cover it up but a new one is going in ok and the cost was not that much for the new bush. All journals are ok and all the corrosion that was under the chrome has now been exposed which the shot blaster got off ok as well.

As far as I could see none of the original metal has been touched.

What happened to yours?

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#8
In reply to #6

Re: removal of electroplated Nickel from steel or bronze

03/30/2008 5:33 PM

Hi,

they would not tell me what etchant they use.

It is very likely that the etch attacked the bronze and not only the nickel.

RHABE

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#9
In reply to #8

Re: removal of electroplated Nickel from steel or bronze

03/30/2008 5:42 PM

As I see it, with electro plating or reverse electro plating, you don't need an etch to do the work. You have your solution of the metal ions you want to deposit with 2 electric conductors, one being the part you want to work on. With reverse plating you have the solution without the metal ions in it as you will be enriching the solution while you strip it of the piece. I have not heard of electro plating with etch in this respect.

If they did use an etch and they were aware of the base metal they were working with, they were not very professional about it in my mind. Without the need to go and use another plater, have you asked others what they think about what happened the first time? If you present them with the problem, they will have to give you some explanation why, even if only to convince you that they can do the job.

Either way it sounds like the wrong process was chosen for the job.

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#4

Re: removal of electroplated Nickel from steel or bronze

03/30/2008 3:09 PM

Cu Sn 7 Zn Pb
DIN 1705

2.1090

Hi,

the material is Rg7 as stated above.

Machining is easy and with good surface quality.

We need 300 mm diameter and a complicated shape turned on an ultraprecision lathe with airbearing mainspindle and direct drive.

Tolerance for out of roundness (radial or axial, tilt removed) is 0.4 µm.

So at removing the nickel plating -that is done after turning- we can tolerate 0.2 to 0.4 µm surface deterioration, if introducing only waviness then a little bit more.

RHABE

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#7
In reply to #4

Re: removal of electroplated Nickel from steel or bronze

03/30/2008 5:30 PM

RHABE,

An illustration or picture would be worth a 1000 words here.

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#10

Re: removal of electroplated Nickel from steel or bronze

03/31/2008 2:02 AM

Thank you for comments.

I will try to get more information from 2 other electroplaters

and tell here if successful.

RHABE

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#11

Re: removal of electroplated Nickel from steel or bronze

03/31/2008 9:30 AM

Rhabe,

Typically, nickel coatings are removed from substrates of aluminum, brass, copper, steel and zinc die cast by the following method:

  1. Prepare a solution with 600 ml/l of sulfuric acid added to water
  2. Bath is cooled to room temperature
  3. Use a lead cathode (neg DC)
  4. Rectifier is set a 6 volts DC (or less demending on part size and geometry)
  5. Parts are made anodic (pos DC)
  6. Submerger live current into sulfuric acid solutions and agitate
  7. Monitor closely
  8. Over stripping can pit the substrate so careful monitoring is required
  9. Nickel deposit is thicker at the high currrent densisty areas and may require more time and a reduction in voltage. Gassing will occur since the work is anodic. If the parts are racked, it is easily viewed but if they are placed in a barrel it may be more difficult to monitor the stripping process
  10. Once stripping is complete, substrate will require a slightly acidic post dip to remove smut.

Electroplating chemical companies like Macdermid Inc. www.macdermid.com/industrial) (+1 203.575.5700) provide stripping products that contain inhibitors to protect the substrate from being etched.

I hope this helps...depending on the size of the part and its geometry, try stripping a sample before subjecting the whole lot to this procedure.

Good luck,

Rich

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#12
In reply to #11

Re: removal of electroplated Nickel from steel or bronze

03/31/2008 12:39 PM

Thank you!

Do you know the recommended current density?

RHABE

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#13
In reply to #12

Re: removal of electroplated Nickel from steel or bronze

03/31/2008 3:15 PM

Rhabe,

Not knowing much about your part, I would suggest that you set your rectifier at 6 Volts before you lower the parts into the stripping solution. This should provide the most consistant results.

Rich

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#14

Re: removal of electroplated Nickel from steel or bronze

03/31/2008 9:50 PM

RHABE,

If the substrate surface was "precision machined" and has since been coated, is it possible to repeat the machining process to remove the deposited layer?

This question is being asked since you have hinted that the coating may not be nickel.

Our electroplating contractor guarantees that there will be irregularities in the deposited thickness when plating is done. It would seem there would be similar irregularities in the reverse process.

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#15
In reply to #14

Re: removal of electroplated Nickel from steel or bronze

04/01/2008 12:45 PM

Hi,

remachining would be possible but cost too much and reclamping seems to be impossible

as the allowed radial and tilting runout is below 0.5µm or 20µinch.

We would change the coating if a better (smoother) surface and removal would be possible with other coatings.

We tried electroless nickel that is said to have much less irregularities, this ok, but removal also not ok.

Thank you

RHABE

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