The effect of Al content on the galvanic corrosion behaviour of coupled Ni/graphite and Ni–Al coatings

In this study, the corrosion behaviour of 75Ni/25graphite abradable coating and Ni–Al bonding coatings with different Al content were investigated with open circuit potential and polarization tests. The galvanic corrosion of the coupled Ni/graphite and Ni–Al coatings was studied by using a zero-resistance ammeter in 5 wt% NaCl solution. The experimental results showed that the corrosion resistance of the Ni–Al coatings decreased with increasing Al contents. In the galvanic corrosion test, the Ni–Al coatings with high Al contents (80Ni–20Al, 85Ni–15Al, and 90Ni–10Al) were the anodic element of the couples, while, the 95Ni–5Al acted as the cathode element in the couple.

Research highlights
► We study the galvanic corrosion behavior of the coupled Ni/graphite coating and Ni–Al coatings.
► Corrosion resistance of the Ni–Al coatings decreased with increasing Al contents.
► In the galvanic test, Ni–Al coatings with high Al contents were the anodic element of the pairs.
► The 95Ni–5Al acted as the cathode element in the pair.
► These results may be facilitating to design the abradable coating systems.