Optimization Studies on Electroless Nickel Coatings: A Review

1. Introduction

Electroless coatings, developed by Brenner and Riddell (1946) are formed as a result of a chemical reaction between reducing agent present in the solution and the metal ions. The reducing agent reduces the metallic ions in the solution while itself getting oxidised. In contrast to the electro-deposition method, electroless nickel requires no external source of electricity. Continuous build-up of the deposit occurs as the metal being coated; itself acts as the catalyst for the reaction. Large variety of electroless nickel coatings exist as defined by their composition, each having its unique set of properties. Hence, application of electroless nickel can be found in virtually every industry (Brenner & Riddell, 1947). The significant properties of electroless nickel coatings are enlisted in Table 1.

Innumerable advantages in application of electroless nickel have been perceived by the industry for the last five decades. At present, except for some minor hitches, the benefits and attributes for electroless nickel alloys and their technologies are well defined, understood and accepted by many industries who utilize the deposits for a variety of applications. The industrial uses of electroless nickel especially the nickel/phosphorus alloy has grown steadily during the last decade, mainly because of its corrosion and wear resistant properties. Moreover, some recent uses of electroless coating include application in the fields of engineering (Mallory & Hadju, 1991), surface science (Domenech, Lima, Drago, De Lima, Borges, & Avila, 2003), separation and purification technology (Huang, Wei & Chen, 2003) and the likes (Krishnan, Praveen,Ganesan, Kavimani, John, & Srinivasan,2006). Electroless nickel processes can produce a wide variety of deposit types. This versatility has helped electroless nickel to carve out a niche in the coating technology market (Mayer, 1993).