Corrosion properties of Fe-Cr-Nb-B amorphous alloys and coatings

Abstract

In the present work, we report on the corrosion properties of the Fe60Cr8Nb8B24 (at.%) alloy produced using pure and commercial materials in the following conditions: amorphous ribbons, partially crystallized ribbons and coatings produced by spray deposition and powder flame spraying process, in this case LVOF (low velocity oxygen fuel). The amorphous ribbons showed excellent corrosion resistance with formation of a stable passive film that ensured a very large passivation plateau. The (LVOF) coatings presented high fraction of amorphous phase with a layered structure, high porosity (16.2%) and low oxidation level (similar to 0.1%). The spray formed coatings presented crystalline structure with low porosity (1.9%) and low oxidation level (similar to 0.1%). The coatings showed higher corrosion current densities (up to two orders of magnitude) compared to the amorphous ribbons of the same composition for all pH. This deterioration in the corrosion properties were found to be impaired by the presence of crystalline phases. (C) 2014 Elsevier B.V. All rights reserved.