Corrosion Inhibition of Iron and Copper in Chloride Solutions by Benzotriazole

Benzotriazole is shown to be a good corrosion inhibitor of iron in acidic solutions even at chloride ion concentrations of 3.5% NaCl. The corrosion potential of copper in deaerated 1N H₂SO₄ shifted about 300 mV in negative direction to the reversible hydrogen potential with addition of 3.5% chloride ions. In the presence of benzotriazole, addition of chloride ions did not shift the corrosion potential to the reversible hydrogen potential. It is surmised that trace amounts of oxygen cause the noble corrosion potential of copper.