Corrosion of Mild Steel in Molten Sodium Nitrate–Potassium Nitrate Eutectic

AbstractThe corrosion (oxidation) of mild steel in molten NaNO3–KNO3 eutectic has been investigated at temperatures ranging from 250° to 450°c, for exposure periods up to 8 h. The results of both weight-gain and potential measurements revealed the formation of a passivating film consisting mainly of Fe3O4. The thickening of the oxide film proceeds according to a parabolic law, at a rate depending on the temperature of the melt. The activation energy of the process was estimated to be 71·3 kJ/mol. A break was observed in the parabolic plots at higher temperatures; this may indicate the beginning of the passivation process. The results have been discussed in the light of oxidation kinetics data for iron in both molten nitrates and air at higher temperatures.