Investigation on the characteristics and mechanism of AZ80A magnesium alloy corrosion by Halon 1301 and CF3I

Abstract

In order to study the application of gas fire extinguishing agents in civil aircraft fire extinguishing systems, the corrosion characteristics and mechanisms of Halon 1301 and CF3I on AZ80A magnesium alloy were comparatively analyzed. The experimental methods combined with density functional theory were applied to explore the corrosion mechanism. The results indicate that Halon 1301 and CF3I exhibit good compatibility with AZ80A magnesium alloy through physical adsorption at room temperature and pressure, where Halon 1301 has a more stable adsorption configuration. However, with increasing temperature, pyrolysis reactions occur leading to the formation of fluorine containing corrosive substances which can react with magnesium alloy to generate the corrosion production of MgF2 and coke. Although MgF2 and coke can partically reduce reaction rates and protect against corrosion, the presence of MgF2 promotes further pyrolysis, generating more corrosion products. Consequently, the accumulation of corrosion products leads to a loss of metallic luster and a decline in mechanical properties of magnesium alloy along with interfacial cracking due to mutual extrusion between MgF2 and carbon deposition layers. These studies offer theoretical guidance for utilizing CF3I in civil aircraft fire extinguishing systems while facilitating rapid screening for efficient clean gas extinguishing agents.