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

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 E-OCP 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.