LOW MANGANESE CORROSION-RESISTANT STEELS

It has been found that lowering Mn content in steels to 0.2% doubles the beneficial effect of increasing Cr content. The authors have compensated for the absence-of Mo by an increase in Cr content and additional alloying with Ti or Si to retain good resistance of the modified steels against pitting corrosion. The article gives the results of electrochemical measurements of the pit nucleation potential, Enp, for the materials investigated in 0.5 M NaCl at 25°C. In both groups of steels the most susceptible places for pit nucleation are (Cr,Mn)Sx inclusions or TiSx inclusions in Ti bearing steels. The low Mn steels were more resistant to pitting corrosion. Local effects on inclusions in the modified steels are so important for their pitting resistance that they obscure a possible influence of Mo<1.2%.