Comparative study on corrosion behaviour of plasma sprayed Ni–3Ti and Ni–3Al coatings

Abstract

Ni–3Al and Ni–3Ti alloys were deposited on AISI 1045 steel substrate using air plasma spraying process. In this regard, mechanically alloyed feedstock powders were used. Open circuit potential EOCP measurements and Tafel polarisation tests were carried out to study corrosion behaviour of the coatings in 3·5%NaCl solution. These tests indicated that the corrosion performance of the Ni–3Ti coating is better than that of the Ni–3Al coating. The corrosion current densities were three times lower in the Ni–3Ti coating than in Ni–3Al coating. In addition, Ni–3Ti coating showed better passive behaviour than Ni–3Al coating. After 10 h of immersion, the surface of Ni–3Al coating became pitted, and rust spots appeared on the surface. In contrast, there was no rusting and pitting on the surface of Ni–3Ti coating even after 10 h of immersion.