ASTM B733 : 84

1.1 This specification covers requirements for autocatalytic ( electroless) nickel-phosphorus coatings applied to metallic products for engineering (functional) uses from acid-aqueous solutions.

1.2 The coatings are alloys of nickel and phosphorus produced by autocatalytic chemical reduction with hypophosphite. Because the nickel deposited is a catalyst for the reaction, the process is self-sustaining. The chemical and physical properties of the deposit vary primarily with its phosphorus content and subsequent heat treatment. The chemical makeup of the plating bath can also affect the porosity and corrosion resistance of the deposit. For more details, see ASTM STP 265 (1)² and Refs (2) and (3), also refer to Figs. XI. I, X 1.2, and X 1.3 in the Appendix of Guide 8656.

1.3 The coatings are generally deposited from baths operating at pH 4.3 to 5.3 and 85 to 95°C.

1.4 The process produces coatings of uniform thickness on irregular-shaped parts, provided the plating solution circulates freely over their surfaces.

1.5 The coatings have multifunctional properties, such as hardness, heat hardenability, abrasion, wear and corrosion resistance, magnetics, and solderability. They are also used for the salvage of worn or mismachined parts.

1.6 This standard may involve hazardous materials. operations. and equipment. This standard does not purport to address al/ of the safety problems associated with its use. It is the responsibility qf whoever uses this standard to consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior lo use.

1.7 The values stated in SI units are to be regarded as standard.