The effect of a small amount of HCl gas on high temperature oxidation of pure iron and chromium

Abstract

The effect of a small amount of HCl on high temperature oxidation of pure Fe and Cr was examined by thermogravimetry and analysis of corrosion products. Oxidation of Fe at 873K was accelerated slightly by a small amount of HCl whereas the oxidation at temperatures above 973K was restrained by a small amount of HCl. Mass gain of Fe due to oxidation turned negative after an oxidation period of 20ks at temperatures higher than 1073K. Under the condition for which the mass gain turned negative, the formation of volatile FeCl 2 was supposed. On the other hand, the oxidation of Cr at temperatures lower than 1100K was extremely accelerated by a small amount of HCl. At temperatures higher than 1123K, however, the oxidation rate in O 2 containing HCl was the same as that in pure O 2 . It was found that the Cr 2 O 3 scale whose formation was accelerated by HCl contained Cl. Such oxidation behaviors for Fe and Cr under O 2 containing a small amount of HCl were discussed thermodynamically.