Deposition of Ni-Al coatings by pack cementation and corrosion resistance in high temperature and marine environments

Nickel aluminides are ideal materials for protective coatings because they possess high-temperature oxidation resistance and low corrosion rates in marine atmospheres. In this work, a double layered coating was formed by the electrochemical deposition of an initial Ni layer followed by an Al top layer deposited by pack cementation. The coatings were found to contain several Ni-Al on the upper areas and Ni-Fe phases on the substrate/coating interface, as a result of Ni diffusion during the aluminization step. Thermogravimetric high temperature oxidation tests and electrochemical corrosion measurements revealed significant increase of the samples' resistance, compared to the uncoated steel.