Behaviour of S31400 and S32205 steels in HCl‐ and H₂S‐containing gas atmospheres under a low oxygen partial pressure between 480 and 680 °C

Abstract

The effects of gaseous hydrogen chloride and hydrogen sulphide on the hightemperature corrosion of the austenitic SS. S31400 and the duplex steel S32205 were investigated in an atmosphere without molecular O 2 . The testing gas atmosphere consisted of 3.8 vol% HCl, 1.9 vol% CO 2 , 0.3 vol% CO, 2.8 vol% H 2 , 0.02 vol% H 2 S, bal. N 2 . It showed a similar composition, which is present in the thermal cracking of anthropogenic resources. Tests were performed between 480 and 680°C for 1, 3 and 10 days. Mass loss measurements were done for all experiments. After the reaction times the samples showed non-adherent and porous layers of corrosion products, which were investigated by SEM/EDX and XRD. Metallographic cross sections of the corroded samples were prepared by water-free polishing to investigate the microstructure of the corrosion products. Both materials formed large chromium sulphide crystals on top of a chromium oxide layer and a chlorine-containing layer beneath the oxide. The ferrite phase of the duplex steel is selectively attacked, while the austenite phase remained without severe corrosion. Steel S31400 showed a uniform corrosion.

Model About the Course of Corrosion Reactions of Austenitic Steels in H2S-, HCl- and CO2-Containing Atmospheres at 680 °C

“…1c). EDX and XRD analysis identified these crystals as pure FeCl 2 [4,5]. A corrosion mechanism was developed to explain the results obtained during metallographic preparation.…”

“…Most processes work at higher partial pressures of oxygen, where metallic materials are able to form protective oxide layers. However, if chlorine is present, porous and non-protective corrosion layers are formed [1][2][3][4][5].…”

“…During earlier experiments, corrosion resistance of several steels and nickelbased alloys was investigated in H 2 S-and HCl-containing atmosphere at high temperatures [4][5][6]. The potential for oxidation in the gas mixture was low because CO 2 and no O 2 were present.…”

Effect of Varying H2S Content on High-Temperature Corrosion of Ferritic and Austenitic Alloys in a Simulated Pyrolysis Process of Post-Consumer Plastics

“…Still, thermal cracking is a demanding process for metallic materials, since impurities in the post-consumer plastics, like chlorine containing materials or biological components, yield HCl and H2S respectively during cracking. These two gas components are known to cause high temperature corrosion and, thus, lead to damage of metallic materials [1][2][3][4].…”

“…Yet, investigations about the corrosion of steels at low oxygen partial pressure and in the presence of chlorine and sulfur are rare [2,13]. Only a few authors have dealt with this topic and even found differing results in some cases.…”