Corrosion resistance of thermally sprayed high-boron iron-based amorphous-metal coatings: Fe_49.7Cr_17.7Mn_1.9Mo_7.4W_1.6B_15.2C_3.8Si_2.4

An iron-based amorphous metal, Fe_49.7Cr_17.7Mn_1.9Mo_7.4W_1.6B_15.2C_3.8Si_2.4 (SAM2X5), with very good corrosion resistance has been developed. This material was prepared as a melt-spun ribbon, as well as gas atomized powder and a thermal-spray coating. During electrochemical testing in several environments, including seawater at 90 °C, the passive film stability was found to be comparable to that of high-performance nickel-based alloys and superior to that of stainless steels, based on electrochemical measurements of the passive film breakdown potential and general corrosion rates. This material also performed very well in standard salt fog tests. Chromium (Cr), molybdenum (Mo), and tungsten (W) provided corrosion resistance, and boron (B) enabled glass formation. The high boron content of this particular amorphous metal made it an effective neutron absorber and suitable for criticality control applications. This material and its parent alloy maintained corrosion resistance up to the glass transition temperature and remained in the amorphous state during exposure to relatively high neutron doses.