Effect of Al on the corrosion behavior of low alloy steels in wet/dry environment

The iron rust phase has been analyzed by using EPMA. TEM and alternating cu rrent (AC) impedance methods after wet/dry corrosion tests using 0.5 mass%N aCl solution. The steel containing 0.8 mass%Al showed higher corrosion resi stance than carbon steel in the test. Aluminum was identified in the spinel oxide of inner rust of Al-bearing steel by TEM and EPMA. which is confirme d by thermodynamic calculation (Pourbaix analysis). By AC impedance it is d emonstrated that the resistance of the rust ( R-rust) corresponds to the st ructural factor of the rust of steels. The R-rust value of Al-bearing steel increases after the continuous formation of inner rust, which implies that Al takes part in the conversion of spinels into line structure that preven ts the penetration of Cl-ions.