The influence of oxide adherence on the hot-salt corrosion of mild steels

Abstract

The corrosion of pure iron and some mild steels by sodium chloride has been investigated in the temperature range 600 to 900° using hot-stage microscopy, a vibration technique, and quantitatively by means of a vapor exposure test. It has been found that for corrosive attack to occur it is necessary for the sodium chloride to have access to the metal surface, and that such access may be prevented by the presence of an adherent, impervious, scale layer at the metal surface. Such a layer was found to be present on an EN2 steel examined but was not formed on any of the other materials tested. The EN2 steel contained 0.2 pct Ni, and 0.21 pct Si, and both have been shown to become concentrated in the scale at the scale-metal interface. This produced an inner adherent scale which was resistant to sodium chloride penetration and which gave the material an appreciably enhanced corrosion resistance.