Effect of substrate on metallographic corrosion of cladding in stainless/carbon steel bimetal plate

The effect of substrate on metallographic corrosion of cladding in stainless/carbon steel bimetal plate is investigated in this paper. The metallographic observation results show that the presence of substrate (carbon steel) would lead to the over-corrosion of stainless steel grain boundary, interfering with the metallographic observation results of stainless steel. The over-corrosion of stainless steel grain boundary could be attributed to the iron ion released from carbon steel. The excessive iron ion would enlarge the difference of iron ion concentration between etchant and stainless steel grain boundary, forming the concentration cell. The concentration cell would promote the localized corrosion of stainless steel, aggravating the corrosion degree of stainless steel.