Effect of alloying elements on the polarization behaviour of low carbon steels

Polarization studies on four laboratory made steels were conducted. These steels were (i) A plain carbon steel, (ii) Plain carbon steel alloyed with Cu,Cr and Ni, (iii) Plain carbon steel alloyed with Cu,Cr, Ni and Al and (iv) Plain carbon steel alloyed with Cu,Cr,Ni and Mo. Potentiodynamic studies, corrosion rates by weight loss method, and metallography of the steels were studied. It was observed that when the steel is alloyed with Cu,Cr and Ni, the corrosion rate decreased by 55%. When the steel is alloyed with Cu,Cr,Ni and Mo, the corrosion rate further decreased by 85%. But when the steel is alloyed with 0.5% Al, along with Cu . Cr and Ni the corrosion rate had increased by 130% from 6.5 to 16.4 mpy. The best corrosion rate was observed for the alloy containing Cu, Cr, Ni and Mo.