Brush plating is an industrial electroplating process designed for OEM and repair applications without the use of an immersion tank. Many applications require well-engineered and proven coatings that pose as little risk as possible to both the operator and the environment. Zinc-nickel is a less toxic alternative to cadmium that can be used to repair damaged cadmium, zinc-nickel, and IVD aluminum on high strength steels and it meets the performance requirements of AMS 2451/9(1), BAC 5664(2), and ASTM F 519(3). Zinc-nickel does not require a post-plating, hydrogen embrittlement relief bake and provides excellent corrosion protection - when properly applied.
There is an industry shift to decrease environmental impacts and improve employee safety. Through the application of zinc-nickel with non-drip plating tools, the operator no longer has to come in contact with the chemicals or fumes in the brush plating process – further enhancing the safety of the process and decreasing the environmental risk.
This paper will discuss best practices and new application technologies for brush plating zinc-nickel to meet hydrogen embrittlement and corrosion requirements. Proper plating techniques from preparatory steps to a trivalent chromium-cobalt conversion coating application are described to provide the optimal zinc-nickel deposit.
Electroplating is a coating technique used to apply a metallic deposit to alter the properties of the substrate surface. Traditional electroplating involves submerging a part into a tank of electrolyte plating solution and passing a current between the part and an anode, any area that should not be plated must be masked off. Brush electroplating is a portable method of electroplating localized areas without the use of an immersion tank. This involves using a hand-held anode wrapped in an inert, porous material, a rectifier electrical supply, and electrolyte plating solution which is applied by dipping the wrapped anode or with a pump and physically rubbing the wrapped anode onto the area being plated. The brush plating method only requires masking around the immediate area to be plated. Brush plating is 40-60x times faster compared to conventional tank plating due to higher concentrations of the electrolyte in the plating solution, higher current densities, and constant replenishment of fresh plating solution. Brush plating current densities are typically 2 to 6.5 A/in2 (0.3 to 1 A/cm2) compared to tank plating current densities of 0.013 to 0.032 A/in2 (0.002 to 0.005 A/cm2), which results in the same deposit thickness occurring in a shorter period of time.
