Corrosion Effects of C2F6 and C3H2F6 on Typical Metals Under Simulated Storage Conditions

Hexafluoroethane and 1,1,1,3,3,3-hexafluoropropane (abbreviated as HFC-236fa and R-116, respectively, referred to as C2F6 and C3H2F6 based on their molecular formulas) were selected as the object to study the corrosion effects of gas fire-extinguishing agents on different metal materials in the storage state. Typical metal materials used in storage containers including 304 stainless steel, Q235 carbon steel, 6061 aluminum alloy, H59 brass, and T2 copper were subjected to full-immersion corrosion experiments under simulated storage conditions with high-pressure and alternating high–low temperature cycles. High-definition cameras, a scanning electron microscope (SEM), high-precision electronic balances, an energy-dispersive spectrometer (EDS), and X-ray photoelectron spectroscopy (XPS) were used to explore the corrosion characteristics. The chemical reactions and mechanisms were analyzed. The results indicate the following: (1) A thin corrosion layer appears on the surface of the metal with varying degrees of severity but low prevalence. (2) The corrosion rates of C2F6 and C3H2F6 were comparable and varied in the following order: 6061 aluminum alloy > Q235 carbon steel > H59 brass > 304 stainless steel > T2 copper. (3) C3H2F6 is slightly higher than C2F6 in all corrosion rate values. (4) The corrosion of metal materials is mainly attributed to the reaction between metal elements and the F-containing groups produced by the cleavage of C2F6 and C3H2F6. The generated metal halides in turn catalyze the cleavage of C2F6 and C3H2F6. This catalytic effect may be positively correlated with the reactivity of the metal element. (5) The higher corrosive activity of C3H2F6 compared to C2F6 is attributed to the ease of C–C bond cleavage, catalyzed by metal halogens. This study provides theoretical insights into the corrosion ability of halogenated alternatives as a replacement for halon-based fire extinguishers.