A Review of Corrosion Resistance of Fe-based Amorphous Coatings: Influencing Factors and Enhancing Methods

The structural characteristics of amorphous alloys are short-range order, long-range disorder, and no crystal defects such as grain boundaries and dislocations. Fe-based bulk amorphous alloys own lots of merits including ultra-high hardness and strength, excellent corrosion resis-tance and wear resistance, and low cost, nevertheless exist mostly in the forms of powders, thin strips, millimeter bars, etc. due to low glass forming ability and room-temperature brittleness. This intrinsic shortcoming has become the obstacle to the promotion and application of Fe-based amorphous alloys. Fabricating alloy coatings instead of bulks, despite being regarded as a good solution to this problem, can retain the inherent merits of bulk amorphous alloys, and has found wide application in the manufacturing and remanufacturing fields of petrochemical industry, automotive machinery, and marine engineering. Though high velocity oxy-fuel (HVOF) spraying and air plasma spraying (APS) have been proven competent to coat Fe-based amorphous alloys on surface of steel substrate, the corrosion resistance of the obtained coatings depend on various factors. According to relevant researches, properties of the coating such as amorphous constituents (elements of Cr, Mo, Ni, Nb, etc.), porosity, crystalline phases, oxides generated, and the spraying process including size of particles fed, type of spraying technique, spraying parameters, as well as external factors, all of them influence directly or indirectly the protective effect of Fe-based amorphous alloy coatings against corrosive media. Furthermore, researchers have also acquired helpful outputs in methods to improve corrosion resistance, exemplified by heat treatment, pore-sealing treatment, laser remelting, oxidation treatment, ion injection, and polarization treatment. These achievements benefit largely the practical application of Fe-based amorphous coatings to the corrosion protection of marine equipment. This paper provides a summary of the factors affecting the corrosion resistance of Fe-based amorphous coatings and the measures to improve the corrosion resistance of the coating in the post-treatment. It also gives a brief discussion on the existent problems and the future prospect. © 2021, Materials Review Magazine. All right reserved.