When looking at the chemistry of the Modern Nickel Plating solution, you have to go back to the early 1900’s; 1916, to be more precise. Watts began plating nickel with nickel sulfate, nickel chloride and boric acid. These components are the basis of all modern bright, semi-bright, microporous and high-sulfur formulations used today. While the combination is always the same, the amounts differ some by bath type and manufacture. To compare the original formulation to the bright nickel levels, here are the typical levels:
1916 2013 Range
Nickel Chloride 3.0 Oz/gal 12.0 oz/gal 8.0-16.0 Oz/gal
Nickel Sulfate 32.0 Oz/gal 36.0 Oz/gal 35.0- 45.0 Oz/gal
Boric Acid 3.0 Oz/gal 6.0 Oz/gal 5.0 -7.0 Oz/gal
The original Watts bath provides a matte unrefined gray pitted appearance. The addition of just a few additives provide a ductile bright finish. The function of all the components is as follows: The nickel sulfate provides the proper concentration of nickel ions. The nickel metal content determines the limiting current density for obtaining good deposits. The nickel chloride increases the anode corrosion; it produces harder deposits and increases bath conductivity which allows you to use a lower voltage. The boric acid acts as a buffer for pH control making a whiter smoother more ductile deposit.
Three main additives are used in bright nickels are carrier, brightener and wetter. The carrier is the minor grain refiner and major ductilizing agent. This provides a basis for the brightener and keeps the deposit ductile. The brightener does just that, brightens the deposit by further grain refinement and levels the deposit. The leveling effect is just like paving a road through a mountain range. The valleys are filled into the peaks of the mountains leaving a completely level surface. The deposit has no peaks or valleys, just a smooth surface. The wetter reduces the surface tension of the solution and allows the bright deposit to remain pit-free during the plating process.
There is a major commercial value in using the additives to enhance the appearance while reducing the cost of operation by leveling the deposits and reducing the overall metal required to plate the part. Many types of parts are plated with bright nickel such as automotive trim, luggage, furniture, toys, hand tools, plumbing, lights, wire goods and kitchen appliances. It is hard to believe the modern nickel plating started almost 100 years ago. Most of the innovation in the past several years on bright nickel has occurred in the leveling, ductility, and complete brightness of the plated parts. The modifications in additive families have yielded a faster, bright nickel, pit-free appearance.