Effect of surfactants on the mechanical properties of electroless (Ni–P) coating

Abstract

Electroless nickel (EN) coating is a well established surface engineering process that involves deposition of a metal–metalloid alloy coating on various substrates. The effect of surfactants on the surface roughness, microhardness and microstructure of electroless Nickel–Phosphorus (EN) surface protective coating obtained from an alkaline bath is presented in this paper. In this study the influence of surfactants sodium dodecylsulfate (SDS) and cetyl trimethyl ammonium bromide (CTAB) on the surface roughness, microhardness and microstructure of coated samples are investigated. EN deposits with addition of surfactant SDS and CTAB at a concentration of 0.6 g/l produce a smooth surface and the average roughness value (Ra) is 1.715 µm for SDS and 1.607 µm for CTAB which is less than the Ra value of EN deposit without surfactant addition (1.885 µm). The mean average roughness value (Ra) with addition of surfactant is 1.796 µm. It was found that without surfactant the micro hardness value of as-coated condition was 450 Hv. The micro hardness value increased to 685 Hv with addition of SDS and 675 Hv with addition of CTAB. The complete experimental details, results obtained and their analysis is presented in this paper.