Corrosion Aspects of Iron, Austenitic Stainless Steel and Inconel in High Temperature Water

The available data dealing with corrosion of iron, austenitic stainless steel and Inconel in high temperature water are presented. The mechanism of iron corrosion and the effect of water conditions such as pH, dissolved oxygen, dissolved hydrogen and velocity are reviewed. Maintaining the pH close to 10.5 is beneficial to pressurized water-cooled reactors for all three metal systems. Dissolved oxygen in sufficient quantity may be desirable for carbon steel, but it will release a high concentration of chromates in austenitic stainless steel and Inconel systems. Dissolved hydrogen may have a slight inhibiting effect during the early stages of corrosion of austenitic stainless steel, but has little effect on carbon steel and Inconel. In oxygen-freewater, carbon steel produces a brown-black film of magnetite, austenitic stainless steel a dull film of magnetite and spinel (R₃O₄), and Inconel a dark tarnished film of NiO, spinel (R₃O₄) and R₂O₃.