High-Temperature Corrosion of AISI 316L in Chlorosilane Environments at 550°C

Abstract

High temperature chlorosilane gas streams are used throughout the photovoltaic, polycrystalline silicon, and fumed silica industries as a means to purify, refine, and produce silicon species. These gas streams create a unique corrosion environment due the ability of many metals to form metal-silicides or metal-chlorides depending on the atmosphere. In this study, a method was developed to test AISI 316L stainless steel in a high temperature (550°C) chlorosilane environment by exposing the samples to variable amounts of hydrogen, hydrogen chloride (HCl), and silicon tetrachloride (STC). In this method, the mole fraction of HCl was adjusted to investigate when the transition from silicide formation to chloride formation occurs. Gravimetric and surface analysis was performed before and after exposure, revealing that without any HCl in the system, there was predominately metal silicide formation. As the HCl mole fraction was increased up to about 0.027, there was increasing metal chloride formation and decreasing silicide formation. Above an HCl mole fraction of 0.027, there was predominately chloride formation. The silicide formation was accompanied with a net mass gain due to the relatively low vapor pressure of iron silicide and nickel silicide species. Chloride formation was accompanied with a net mass loss due to the reactive evaporation of iron, nickel, and some chromium with chlorine. Lastly, the implications of this study as they relate to industrial processes are discussed.

The Time and Temperature Dependence of AISI 316L Corrosion in Chlorosilane Environments

“…Previous work had shown that 316L in chlorosilane environments can form either metal chlorides or metal silicides depending on the relative amounts of STC and HCl in the system (10). Because metal silicides appear to be more protective than metal chlorides, it was determined that the time and temperature dependence of metal silicide formation in chlorosilane environments is more industrially relevant than metal chloride formation.…”

“…Sample preparation and corrosion exposure was done in accordance to the procedure described in our previous work (10). For completeness, it is briefly described here.…”

“…However, he did not report results at other operating conditions or times. We have reported results in which we exposed 316L stainless steel to chlorosilane environments at 550°C with variable amounts of HCl (10). In these studies, we found that in the presence of only silicon tetrachloride and hydrogen, 316L stainless steel forms a metal silicide layer that causes the sample to gain mass.…”

“…Previous studies have looked at the corrosion behavior of austenitic stainless steels in chlorosilane environments at temperatures of 500-550°C and times of 87-100 hours (1,10). Mui used a packed bed reactor at high pressure to create a mixed chlorosilane environment to investigate the corrosion of several different materials of construction.…”

High-Temperature (550–700°C) Chlorosilane Interactions with Iron

“…Additionally, the authors have done some work in the field of chlorosilane corrosion of 316L stainless steel. [19][20][21] Again, this work was largely studying the implications of using 316L in chlorosilane environments rather than investigating the specific mechanisms of corrosion. To the best knowledge of the authors, there are no published studies detailing the corrosion mechanisms of iron in chlorosilane environments representative of industrial processes.…”