Hot-dip Aluminizing of Low Carbon Steel in Al & Al-5wt % Cr Baths

Hot dip aluminizing of low carbon steel is carried out in pure aluminium bath and Al-5wt% Cr bath. The coating is characterized by scanning electron microscopy and chemical composition of the coating is analysed by EDS (energy dispersive spectroscopy) attached to SEM. The coating consists of three regions, viz., outer aluminium topcoat, intermediate Fe-Al intermetallics layer and the base alloy. The intermetallics layer consists of FeAl3 and Fe2Al5 phases. Fe2Al5 is the major phase in the intermetallics layer. The growth kinetics of intermetallics layer is parabolic in nature implying that it is diffusion controlled. Addition of chromium forms Al7Cr dispersed intermetallics phases in the aluminium topcoat. Addition of chromium has no influence on the morphology of the intermetallics layer. Scratch resistance of the coating is carried out to evaluate the scratch hardness of the coating. Chromium addition improves scratch resistance of the coating.