Influence of a Zwitterionic Surfactant on the Surface Properties of Electroless Ni–P Coating on Mild Steel

Abstract

Abstract3‐(N,N‐Dimethyl myristyl‐ammonio) propane sulfonate zwitterionic surfactant (C14‐SB) which possessed both positive and negative charges was evaluated in the electroless Ni–P coating process. It was observed that the deposition rate, morphology and microhardness of the deposits were enhanced by the addition of C14‐SB surfactant. The excess attractive forces from the negative head of C14‐SB were strong enough to draw metallic nickel particles towards the substrate. Ni particles attempting to deposit on the electrolyte container were eliminated by the repulsive force from the positive head of the surfactant monomers. Thus, the deposition rate of the coating process was improved. The surfactant at its critical micelle concentration (CMC) doubles the deposition rate when compared to the substrate without surfactant. In addition, the microhardness of the deposit at the surfactant CMC increased by 62 %. The corrosion rate of the substrate without surfactant was 7.15 mpy, while it was 3.97 mpy for the substrate deposited with C14‐SB zwitterionic surfactant at the CMC.