Corrosion of 316L Stainless Steel in High Temperature Water and Steam: Mechanisms of Corrosion

316L stainless steel was exposed to 320°C hydrogenated or aerated water and 480°C steam for up to 72 h to determine the aqueous corrosion mechanisms. The thermodynamics of the corrosion process are interpreted using a new concept called the excess volume which predicts stable formation of pores in the inner oxide layer. Corrosion rates are found to be correlated with inner oxide porosity. Inner oxide thicknesses were measured, and thermodynamic modelling was used to determine that the rate-limiting step of corrosion is fluid transport of oxygen via pores in the inner oxide layer.