Tri Nickel Plating

Tri Nickel Chrome Plating

Nickel plating is an important electro deposition process for preserving steel, brass and other basis metals from corrosion. Plated as a bright deposit often combined with chromium, nickel is the most effective electroplated coating for preserving a decorative appearance for extended periods of time in corrosive environments. Nickel electro deposition is also popular for engineering applications as a non-decorative functional plate.

Bright nickel electroplated for decorative uses differs appreciably from non-decorative nickel deposits. The high sulfur content (>0.05%) of the bright deposit reduces its ductility and corrosion resistance. Bright deposits are typically deposited from the watts formulation (see below) with the addition of organic-sulfur brightening systems. Functional deposits are typically deposited from the watts bath without the addition of brighteners (commonly referred to as watts non-bright) or from sulfamate nickel chemistries (see below).

Brightness in nickel deposits is induced with organic-sulfur compounds that decompose at cathode surfaces forming very small particles of nickel sulfide which refine the grain size of the deposit at the cathode surface (plated part) by at least two orders of magnitude. The selection of brightener additions to the plating bath affects ductility, internal stress, electrical conductivity and corrosion resistance of the deposit, all in a negative manner. Nickel coatings stressed in tension reduce the fatigue strength of steel. Nickel deposits lose corrosion resistance, ductility and electrical conductivity as the amount of co-deposited sulfur or other impurities increases from the brightening system. The change of the above characteristics is a rather complex subject which is primarily dependent on the bath chemistry, but also to a lesser extent on the operational parameters of that chemistry. The following charts will provide general trends/properties of nickel as deposited from the three (3) traditional chemical systems: watts non-bright, watts bright (watts with organic brighteners) and sulfamate.