The corrosion behavior of four commercial steels in reducing atmospheres containing HCl at 773-873 K

The corrosion of four Fe-Cr commercial steels with different tents in a simulated waste-gasification atmosphere containing 0.5 vol.% H-2, 0.5 vol.% HCl, balance CO2 has been investigated at 773 and 873 K. The same materials have also been tested in the same gas mixture free from HCl at both temperatures for comparison. The results show that the materials with low-chromium content (2.25 CrMoV and NF616) undergo accelerated corrosion in the presence of HCl, while the stainless steel SS304 suffers very little corrosion. On the contrary a steel containing 12 wt.% Cr (12 CrMoV) corrodes rather rapidly at 773 K but quite slowly at 873 K. The beneficial effect of chromium on the corrosion resistance of the steels increases with the chromium content at both temperatures. The steels tested show corrosion rates generally decreasing with time, having kinetics which are approximately parabolic at 773 K but intermediate between parabolic and linear at 873 K Only little or even no chlorine can be detected at the scale/metal interface at both temperatures for all materials corroded in HO-containing atmospheres. The corrosion mechanism can be explained by the so-called active-oxidation, model.