I'm working on electroplated diamond tools. Watts Bath is used for such kind of process. After plating has finished I need to remove that plated Nickel layer completely. I have used reverse current to remove this layer so far but when I use reverse current I see micro holes on my sample just because of current. I think some chemicals can work for removing it or you can suggest me any other way. I appreciate for your answers .
I write the following 3 methods; hope any one will help.
[1a] Soak a clean cotton cloth in vinegar; wring out the excess, and thoroughly scrub the dirtied areas of Ni plating with the vinegar-soaked cloth. You may need to re-soak the cloth after scrubbing for a while.When finished, wipe excess vinegar off Ni plating by passing a soft cloth soaked in water over the area.
[1b]For stubborn stains, soak Ni plated piece instead of simply wiping it down. Combine four parts water with one part vinegar in a container large enough to soak the piece in. Do not use straight vinegar, since it is often too abrasive to expose to thin Ni coatings for extended periods. Soak the Ni plated item in the solution for several hours to overnight. Upon pulling it out, wipe the dirt and tarnish off with a cloth and rinse the Ni under clean water to remove any traces of vinegar.
[2a] If the tool does not contain Cu/ its alloy, apply straight NH3 (pure NH3 not diluted).It is very effective but it can also be very damaging to Ni plating if the plating is allowed to sit in it for too long. Pour NH3 in a container and dip a scouring pad into it.Vigorously rub the dirtied area of the Ni with NH3-soaked pad rinse with H2O.
[2b]For a more intense cleaning of the item having no Cu/ its alloy, combine equal parts H2Oand NH3 into a bucket . Allow Ni plated item to soak in this solution for 30 minutes before brushing at the stain or dirt with a toothbrush. When done, rinse the item under clean water. Never perform this with straight NH3 or for more than 30 minutes at once, since the harsh nature of NH3 will cause the plating to chip and flake off.
[3]The easiest way to remove Ni plating is with a fairly strong sulfuric acid solution; say 50% with about 5% of glycerine added as a fining agent.
Manohar,
Thanks for detailed answer. The key point is there not to harm steel coupon, i want to reuse my steel coupon. I will try to implement the last suggestion that you advised but i think it will take more than half an hour to remove that layer. By the way i wonder in what way these acids will effect my steel coupon in terms of mechanical properties?
Must read the following given paragraphs. The lines written in capital letters may help you.
H2SO4 IS CAPABLE OF RESPONDING IN MANY DIFFERENT WAYS AS ITS REACTION ON STEEL CAN SOMETIMES BE CONTRADICTORY. At certain concentrations, H2SO4 on steel will form a protective layer and the steel will be fine while other concentrations will yield corrosion and the steel will slowly deteriorate.
The best reaction of H2SO4 on steel is that it begins to create an iron sulfate layer that protects the steel from the acid and causes no corrosion and little metal loss. THIS WILL OCCUR ONLY IFTHE H2SO4 CONCENTRATION IS INBETWEEN 70-99.5%. AT A CONCENTRATION IN THIS RANGE, H2SO4 CAN BE STORED IN A NON-PROTECTIVE AND UNLINED STEEL CASE.
As with most substances, the more common reaction of H2SO4 on steel is corrosion. Regardless of whether the concentration is lower or higher than the safe concentration range, sulfuric acid will begin corroding the steel. The corrosion typically is slow, but very high concentrations may quickly eat through the steel. To hold H2SO4 at the safer concentrations, a steel case lined with iron sulfate should be used, and the lining should be replenished as needed, if possible.
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