Effect of surfactant on the alumina dispersion and corrosion behavior of electroless Ni-P-Al₂.O₃ composite coatings

Electroless Ni-P-Al₂O₃ composite coatings have been synthesized on mild steel shafts using surfactant cetyltrimethyle ammonium bromide (CTAB) as dispersant. The effects of the surfactant on the alumina dispersion, weight fraction in coatings, and corrosion resistance ofthe composite coatings under salt spray test were investigated. Results showed that alumina dispersion was improved, whereas weight fraction was decreased, with the increasing concentration of the dispersant CTAB.The corrosion resistance of the composite coatings was found to increase with the increase in CTAB concentration up to a certain optimum of 20 mg/L, beyond which a decreasing trend of corrosion resistance was observed under salt spray test. Compared with Ni-P coating, all the Ni-P-Al₂O₃ composite coatings showed improved corrosion-resistant properties.