Aluminum electroplating on steel from a fused bromide electrolyte

A quaternary bromide bath (LiBr-KBr-CsBr-AlBr₃) was used to electro-coat aluminum on steel substrates. The electrolyte was prepared by the addition of AlBr₃ into the eutectic LiBr-KBr-CsBr melt. A smooth, thick, adherent and shiny aluminum coating could be obtained with 80wt.% AlBr₃ in the ternary melt. The SEM photographs of the coated surfaces suggest the formation of thick and dense coatings with good aluminum coverage. Both salt immersion and open circuit potential measurement suggested that the coatings did display a good corrosion-resistance behavior. Annealing of the coated surfaces, prior to corrosion tests, suggested the robustness of the metallic aluminum coating in preventing the corrosion of the steel surfaces. Studies also indicated that the quaternary bromide plating bath can potentially provide a better aluminum coating on both ferrous and non-ferrous metals, including complex surfaces/geometries.