Electroless nickel plating is an autocatalytic process and does not use externally applied electric current to produce the deposit. The electroless process deposits a uniform coating thickness, regardless of the shape of the part or its surface irregularities.

This uniform hard deposition provides protection from from oxidation, corrosion and wear.

Low-phosphorus electroless nickel yields the brightest and hardest deposits. Hardness ranges from 60-70 RC. Low-phosphorus content improves soldering and brazing performance. low-phosphorus electroless nickel plating conforms to ASTM 733 B, Type III, and MIL-C-26074 as described in the specification summary.

Medium-phosphorus or mid-phos is the most widely used electroless nickel bath. If phosphorus content is not specified, mid-phos will likely be chosen by the finisher. The hardness is typically 40 RC. Porosity is lower, and conversely corrosion resistance is higher than low-phos electroless nickel. Nu-Metal’s mid-phosphorus electroless nickel plating conforms to ASTM 733 B, Type IV, and MIL-C-26074 as described in the specification summary.

High-phosphorous electroless nickel is dense and dull in comparison to the mid- and low-phosphorus deposits. High-phosphorus exhibits the best corrosion resistance of the electroless nickel family; however, the deposit is not as hard as the lower phosphorus content. Hardness may be improved by heat treating. High-phosphorus is a virtually non-magnetic coating. Hudson Plating’s high-phosphorus electroless nickel plating conforms to ASTM 733 B, Type V and MIL-C-26074 as described in the specification summary.

Hydrogen embrittlement relief bake may be required for hard-enable steel and stainless steel. Within 4 hours after plating, coated Class 1 and 2 steel parts which have a hardness of RC 40 or above shall require a bake at 375°C ±25°F for not less than 3 hours. Heat treatments of Class 2 hardness coatings shall have a minimum hardness of 800 Knoop or equivalent. The hardness can be achieved by heating the part in accordance with the schedule given in the specification. Class 3 hardness coatings. Coated non-heat-treatable aluminum parts shall be heated for 1 to 1-1/2 hours at 375°F±15°F (191°C±8°C) to improve adhesion of nickel. Class 4 coatings. Coated heat-treatable aluminum alloys shall be heated between 240°C to 260°F (116°C to 127°C) for 1 to 1-1/2 hours to improve adhesion of nickel.

All analytical and testing compliance is performed by the HPW in-house laboratory. Thickness and adhesion verification, hardness of electroless nickel plated deposition, cross-section thickness analysis, hydrogen embrittlement relief, corrosion resistance (salt spray), solution analysis, and composition (phosphorus) testing are a sample of Electroless Nickel plating specification requirements. Inspection and testing are completed and documented for assurance of compliance to all specification and customer requirements.