Variation in thickness of nickel plating
A discussion started in 2002 & continuing through 2017 -- add your Q to bring it back to the Hot Topics page.(2002)
Q. In a large scale automatic installation for multi-layered nickel plating on MS substrate, wide and wild variation in thickness of nickel deposit is encountered. thickness varies from 8-40 microns for average thickness of 20 microns. There is a variation from component to component & also on component itself. the variation is also noticed on a surface which is almost parallel to anode surface. Kindly throw some light as to which factors besides jigging, can have this influence on thickness distribution. can chemistry of the bath/additives play any significant role in this case? Thickness is measured by magnetic gauge.
- Mumbai, Maharashtra, India
A. Hi. D.T. I've never heard of additives wrecking the thickness distribution, but you should plate a panel in a Hull Cell and test the thickness distribution to see what you find. Good luck.
Ted Mooney, P.E. RET
Pine Beach, New Jersey
There are several reasons for non uniform nickel deposit.
1) Check distance between anode and cathode, need certain distance.
A. Factors that can affect the thickness distribution are numerous. You correctly identify jigging, but there is also tank loading, bath pH, current density, screening, shielding etc. If the tank is overloaded you will have parts screening other parts, so you will get poor reproducibility. If the bath is too low pH, then you encourage hydrogen evolution and this can selectively replace metal deposition. If the parts are not jigged correctly, you will get preferential current passage. If multiple jigs are used, the resistance of each path will affect the current and hence the thickness. As Ted says, do a Hull Cell and see what that tells you about he chemistry of your system. If that is OK it must be the electrics and/or the tank geometries
R&D practical scientist
Chesham, Bucks, UK
June 27, 2017
Q. While electroplating a case of a watch with Ni the top surface gets a coating of 9 microns where as bottom gets 7 microns it is in a jig which is rotating on itself and also the case.Ajay Prasad
Student - Chennai,Tamil Nadu, India
Ed. note: For a deeper and more theoretical discussion, please see letter 3795 "How to overcome non uniform thickness of coating in electroplating"