Amorphous Metallic Coatings with Tunable Corrosion Properties Based on Al-Co-Ce-(Mo) Alloy Compositions

Selected corrosion properties of the recently developed amorphous Al-Co-Ce alloy system are reported. Improved resistance to halide-induced pitting was observed in near neutral solution when the fully amorphous alloy and an aged alloy (100°C for up to1000 hrs.) were compared to high purity aluminum. Both the open circuit potential and the repassivation potential were found to be strongly influenced by the concentration of cobalt in the alloy. Tunable corrosion properties based on pre-selection of Co content is shown to be feasible. This alloy system also showed improved resistance to rapid dissolution in alkaline solutions, in contrast with the behavior of pure aluminum. However, in acidic solutions the dissolution rate of the amorphous alloy was increased when compared to pure aluminum. These unique properties of the amorphous alloys remained after structural relaxation and/or partial devitrification by low temperature heat-treatments at 100°C. However, complete recrystallization by 550°C heat treatment removed all benefits seen in amorphous variants.