Study of influence of manganese additions on electrochemical corrosion behaviour of austenitic spheroidal graphite iron

Abstract

The effect of the progressive replacementof nickel by manganese on the electrochemical corrosion behaviour of austenitic spheroidal graphite iron has been investigated in 5% solutions of NaCl, NaOH, and H₂SO₄ using potentiodynamic polarization and metallographic studies. The change in corrosion rate in the substituted alloys depends significantly on the corrosion medium. The results indicate that up to 15%Ni can be effectively replaced by ∼ 8%Mn+2%Cr with relatively small sacrifice of corrosion resistance in 5%NaCl and 5%NaOH media. however, there is a significant loss of corrosion resistance in 5%H₂SO₄ when manganese is added. The addition of 1,2,3 benzotriazole inhibitor improved the corrosion resistance in the acid medium. The role of microstructure on electrochemical corrosion is discussed using metallographic observations and polarization results.