Failure analysis of the tyre valves of trucks

• The failure cause of tyre valves was investigated.
• Higher content S and O were detected.
• Intergranular morphology and branch cracks were observed.
• Failure of the air valves was caused by SO2 SCC.
• The necessary conditions for SCC were satisfied.

In this case study, the failure cause of the tyre valves of trucks was investigated. Higher content sulphur and oxygen were detected by analyzing the corrosion products. The intergranular cracking morphologies were observed by SEM. The branch cracks were shown by metallographical and SEM observations. Residual stress was verified by hardness testing. Synthesizing all the experimental results the failed air valves were considered to be caused by sulphur dioxide SCC. The three necessary conditions for SCC were satisfied in this case study: susceptible brass alloy, corrosive media (SO2) contained in the surrounding environment, and sufficient tensile stress. In the end, some important suggestions were proposed to prevent the similar failures in the future.