State of Art Review on Nickel-Based Electroless Coatings and Materials

Surface coatings are widely used in various industries to improve the functional performance and robustness. Researchers considered the electroless-coating technique is one of the prominent methods in the past decade due to its simplicity, low operating temperature, pores-free, optimized cost and low processing time. Electroless plating is one step method and its properties are influenced by various parameters such as bath temperature, pH value, and type of surfactant used, concentration of nickel source, reducing agent and secondary nano/micro particles added to the bath to form composite coatings. The present review aims at the study of various coating materials and existing techniques in the preparation of electroless Ni coatings for ferrous and nonferrous materials. More focus on Ni–P, Ni–B, and its composite coatings which are formed by co-deposition of micro (hard) and nano (soft) particles in Ni–P, Ni–B matrix. The influence of process parameters such as heat treatment temperature, reducing agent concentration, type of surfactant, reinforcement material property (particle size) to improve mechanical behavior namely hardness, wear, friction coefficient, high-temperature oxidation behavior and environmental protectivity (corrosion/erosion) have extensively studied and well-described.