Can anyone explain about open circuit potential of copper coated steel zinc coated steel and carbon steel in soil under same conditions. Why OCP of copper and zinc coated steel is more than carbon steel tested in soil?
May be due to more cathodic protection of carbon steel as compared to Cu and Zn in soil.
Please look at the relative REDOX (emf) of each metal. The answer is likely that they oxidize or are oxidized differently, with Iron being the highest oxidant.
Dear Shahrukh When the soil contain some of organic substances and these substances were readily adsorbed on the surface of the uncoated steel and the surface of copper or zinc coatings and able to form a continuous inhibition layer. This layer may able to shift the open circuit potential in the positive direction. Also, the presence of the microbial activity produced by the sulfur reducing bacteria SRB in the soil is able to cause the ennoblement of the substrate due to the biofilm formation. In both above cases the galvanic process between the zinc or copper coating layer and steel substrate become a limited and the observed difference in potential between the steel and coated steel comes from the protection value of the zinc and copper coatings. Best regards
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