Mechanism of Corrosion of Carbon and Low Alloy Ferritic Steels by High Temperature Water^✫

Experimental evidence indicates that up to 90% of all hydrogen is generated at the metal/oxide interface during the corrosion of carbon and low alloy ferritic steels by high temperature water, in the absence of oxygen. None of the presently accepted mechanisms are able to account for this observation. After consideration of possible diffusion routes, a mechanism involving diffusion of H₂O and/or O²⁻, H⁺, and Fe²⁺ is proposed to account for the experimental findings. The relationship between the amount of magnetite deposited from solution onto the surface and the fraction of hydrogen generated at the metal/oxide interface is discussed in terms of the proposed mechanism.