Effect of aluminium on electrochemical corrosion behaviour of Fe-0-5Cand Fe-1Calloys in 0.25M H2SO4

Electroslag remelted iron-aluminium alloys, with carbon contents of 0.5 and 1 wt-%, were used to investigate the effect of Al on the electrochemical corrosion behaviour in 0.25 M sulphuric acid solution. The alloy compositions were (wt-%): (I) Fe-16Al-0.5C, (2) Fe-10Al-0.5C, (3) Fe-8Al-0.5C, (4) Fe-16Al-1C, (5) Fe-10Al-1C, and (6) Fe-8Al-1C Lowering the Al content of the alloys resulted in a deterioration of the passivation behaviour during potentiodynamic polarisation testing. This deterioration vas attributed to the reduced Al content of the matrix phase on lowering the Al content of the alloy. Examination of the polarised surfaces via SEM revealed that in high Al content alloys carbides are preferentially attacked, while in low Al content allo, vs the attack is more general. Alloys with a carbon content of 1 wt-% displayed somewhat inferior passivation tendencies compared with those of alloys containing 0.5 wt-% carbon