Choosing the Right Nickel for Your Brush Plating Application

Today’s demanding industrial applications require well-engineered and proven deposits that pose as little risk as possible to both the operator and the environment.

Brush plating can be used to apply a variety of nickel deposits including nickel acid, nickel high-speed and sulfamate nickel as well as a multitude of other metals and alloys. And the requirements of the application will determine the type of nickel deposit you select.

Nickel acid – primarily used as a preplate, but is also used as a prebraze coating, and for low thickness buildups for dimensional restoration – has a hardness of HRC 36. It is a dense deposit that can plate 125 microns (0.005 in) in one layer. Under normal conditions, nickel acid can be used at room temperature with excellent results. However, when the solution is used for build-up it should be preheated. If not, the deposit will burn easily, plate slowly, and will not plate the thickness expected, but plate deposits that are bright and highly stressed.

Sufficient flow of solution is necessary when plating with nickel acid. Insufficient flow with a small volume of solution, especially when plating at a high current density, can result in overheating at the work area, and burning of the deposit.

Nickel high-speed – used for salvage and dimensional restoration applications – has a hardness of HRC 54, and can be plated up to 375 microns (0.015 in.) per layer. It’s a microcracked deposit and has very poor ductility like nickel acid. While nickel acid performs best when heated, nickel high-speed plates well at room temperature; in fact, heating the solution has no significant effect on plating characteristics or deposit quality. If the solution is used within the recommended limits, a certain number of amp-hours will deposit a certain amount of plating regardless of plating conditions. Although the application of nickel high-speed is relatively easy, a preplate of nickel acid is required for many base materials except copper, copper alloys, zinc and zinc alloys.

Sulfamate Nickels are approved for the highly-regulated aerospace industry. They range in hardness from HV 190 to HV 575 (low stress, low hardness; low stress, medium hardness, and low stress, hard) and their use is application-specific. Sulfamate nickels are used for corrosion protection, dimensional restoration and prebraze. The maximum thickness per layer that can be plated is 375 microns (0.015 in.). Sulfamate nickel is generally characterized as difficult to plate. The solution requires the operator to check the specific gravity prior to beginning the plating operation, then check every 2 1/2 amp-hr (minimum) for each liter of solution being used. Also, the solution must be heated and continuously filtered during use to ensure consistency in deposit properties and to remove fine particulate within the nominal size rating of the filter. As sulfamate nickels are “sliding factor” solutions, the amp-hrs required to plate a certain thickness on a surface area will vary, depending on the freshness of the solution.

Nickel brush plating meets a variety of specifications including AMS 2403, 2424, and 2451/1, 2, 3, 7, and aerospace approvals from Pratt & Whitney, Sikorsky, FMC Technologies, Messier-Dowty, and Solar Turbines.