Effect of surfactants on the corrosion of amorphous 76Ni‐24P alloy in neutral solutions

Abstract

Abstract76Ni‐24P amorphous alloys have been electrodeposited from solutions containing sodium lauryl sulphate (SLS) and triton‐X 100 (TX‐100) to improve the surface quality of the specimens. Corrosion behaviour of electrodeposited amorphous alloys in sulphate and chloride solutions at 25°C has been studied by potential‐time decay, linear polarization resistance and potentiodynamic techniques. Anodic polarization curves show that the specimens exhibit mild passivity at potentials between approximately −200 mV and 200 mV (SCE) and dissolve transpassively above 200 mV (SCE). The sulphate solution was found to increase the dissolution of the samples treated by the surfactants during the substrate brass plating. The nonanionic surfactant increases the corrosion current by 10 times compared to the anionic one which enhances the current by 400 times; the interpretation was based on the enhanced dissolution of the microcrystals of the specimens in the sulphate solution and to the steric hindrance of the surfactants. In addition, the alloys are more resistant to chlorides due to the formation of a phosphate/hypophosphite film which protects the surface from dissolution.