Why is my acid copper plating not adhering to my nickel plated steel?
A discussion started in 2007 but continuing through 2018(2007)
I am a well educated professional chemist and a hobbyist motorcycle restorer.
In pursuit of my restoration endeavors I have been trying to learn how to nickel plate my old motorcycle parts (learning chemistries of all sorts is also my hobby so I insist of doing it myself, I have access to almost any chemical, safety equipment, and proper disposal outlets). My goal is to produce a bright nickel finish on mild steel and cast iron parts. I want to first plate the semi-polished parts with nickel then build up with acid copper for easy buffing prior to bright nickel.
I have experimented with variations of a Watts style nickel sulfate bath, that I concocted from reading patents, academic journals, and web sites. I can achieve nice uniform, semi-bright deposits when plating 1x10 cm mild steel strips (unpolished, activated in dilute HCl/HNO3) in a homemade Hull Cell with my Watts solution at 50 °C, and a current density of about 10-30 ASF with a pure nickel anode. The plate adheres well, what I mean by this is: I can bend the strip back and forth until it breaks without the nickel cracking off, and if you dip the part in acid copper solution no immersion deposits are formed, also you can buff the heck out of them without wearing the nickel off. I get similar results plating copper strips.
Here's the problem: when I try to plate over the nickel layer with my acid copper solution (H2SO4, CuSO4, NaCl) I can get a nice uniform plate under various bath compositions in the Hull Cell, at 10-90 ASF, and 25-40 °C, but the copper cracks off the nickel layer very easy when I bend the strip. I have tried reversing the current on the nickel-plated strip for one minute at ~30 ASF in the copper solution prior to plating and this helps but still seems unreliable. Activating the nickel layer in 30% H2SO4 doesn't seem to help either. I get good adhesion to copper with these baths. Sometimes the copper plate causes sections of the nickel to pull away from the steel base metal as if it has weekend the bond between the nickel and steel but this is less common.
Everywhere I read it sounds trivial to plate copper onto nickel, so why doesn't mine work!?
motorcycle restorer, metal finisher - san francisco, California, USA
A. Hi Jeffrey. It may (or may not) be trivial to plate copper onto fresh nickel plating (plated within the last 15 seconds) but it is not at all easy to plate onto old nickel with proper adhesion. What is worth trying is activating your semi-bright nickel plating with a Wood's Nickel strike immediately before the copper plating. Good luck.
Ted Mooney, P.E.
Pine Beach, New Jersey
A. Hobby plating is not for the meek. You won't get it done any cheaper or better in the long run. Plus the process is messy, dirty and stinky.
Acid copper plating is an enhancement to the final finish, not a short cut in polishing. You just end up putting more copper on than needed which can cause fitting problems with the parts. And despite acid copper's efficiency, it is still subject to the dynamics of electroplating. It will not level out enough to make up for less than ideal polishing. The copper may be soft, but can come out so high density deformed that it turns into an aggravating metal sculpturing job instead.
And just for the record. Reversing polarity in a plating bath is a sure fire way of killing the bath in a short period of time.
- St. Louis, Missouri, USA
Copper plating onto nickelMay 20, 2018
Q. Hi everyone,
i am restoring a couple of single shot .22 rifles, and the final aim is to copper plate the living Sulphur Hydrogen Indium Tellurium out of the receiver and barrel (3-5 mm thick), to the point where it looks like a coral encrusted shipwrecked cannon, except with twinkly copper crystals instead of coral.
I have no problem nickel plating onto steel (caustic boil 30 min, HCl etch, NiCl+citrate, +ammonia)
THE PROBLEM COMES when I stick my nicely nickel plated receiver into CuSO4. I get an immersion/substitution deposit, and the whole thing turns to copper powder, and it is hard to get rid of the copper patches … it is like a virus, I am guessing this is because of the fact that copper is more noble than hydrogen, whereas nickel is less noble than hydrogen.
Once I get a good copper strike onto nickel, I have no problem copper plating from there (CuSO4 + enough sugar to kill a horse as a slowing agent).
SO THE QUESTION IS How the Fluorine do I get a copper strike onto nickel without cyanide or other toxic stuff.
I have access to Citric, Hydrochloric, sulphuric, acetic acids, NaOH, bicarb, ammonia, Manganese sulphate, zinc sulphate, 3V open circuit x7A short circuit, and 75VOC x0.6A SC power supplies, current limiters and voltage droppers,
I have chosen copper as my final layer because it is relatively easy to get hold of oodles of it, but I don't have the money to put that much nickel all over everything.
And a final note, please don't tell me to take it to a professional; I want to do this myself for the sake of learning, and pride.
All security regulations will be followed.
Metal salts will be neutralised and oxides dried kept for later use, NaCl goes down the drain.
Critical pin holes will be plugged with graphite
hobbyist firearms restoring - Australia
September 19, 2018
A. Hi all, I have been experimenting a bit, and have discovered a few different methods, which i will outline in order of viability.
First we have to understand the things needed to inhibit the process of an immersion deposit.
3 concentration of "Blue" ions
CuSO4 is acidic enough to let an immersion deposit occur, it also has way too many blue ions floating around, and it is a relatively small cluster of atoms at 21 atoms, things happen rather quickly, fast enough to trap a hydrogen bubble and a water molecule behind the layer of copper. NOTHING LIKES TO STICK TO WET GAS!
Complexing is easily visualised as a cloud dropping one raindop on a mountain range, and then moving away to make room for the next cloud to drop one more droplet.
So we need a larger acid, something like citric acid, which is a H3 citrate, this immediately means Cu2+ has a hard time fitting into one ion and forms a much larger complex.
We also need to raise the pH,
ERGO Sodium Citrate, plus copper plus electricity. solution goes deep blue, a different colour to our old friend copper sulphate. small scale tests were very promising, but larger scale tests ended up a bit weird.
So lets move on to borax. this has a decahydrate complex, and has a H3 Borate. Right out of the packet it performs very well, solution does not turn blue to speak of, and there is a big win already; it has a high pH, (win no 2), and happens very slowly, (win no 3) -- I even had copper depositing out on the back of my test piece and skipping the front entirely (I'm sure that could be handy).
The downside is that it takes over night for any thing to show, and after extended use the anode jams up with copper borate, which kills the current, but is easily fixed by swapping the polarity for a graphite anode.
Use bicarb to rub off the muck.
Optional extras aren't limited to a pinch of salt, or a very small pinch of CuSo4 to help with anode jam.
This method will strike very well onto steel.
And finally the best solution yet, Sodium Soapy Chloride/Sulphate, i.e., Sodium Chloride with excess NaOH added, or mix CuSO4 with enough NaOH to make things soapy and drop out all those light blue ions. Optional extras are not limited to ammonia, and borax.
The anode will jam up with black, but this does not affect the available current to any discernible degree.
Early tests show this will strike onto UNactivated nickel (wooohoooo!) and every grade of steel I have thrown at it so far.
Again, use bicarb to wipe off the muck
I hope this helps someone.
These chemicals are available at the local supermarket or hardware store,
Hobbyist firearms restoring - VALLEY VIEW, Australia
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