Intergranular stress corrosion cracking of acoustic-filter hooks used in car

Some acoustic-filter hooks used in car fractured in service. The failure mechanism of the hooks is intergranular stress corrosion cracking. The necessary conditions (susceptible composition of the hook materials; presence of chloride in service environment; presence of residual tensile stress and occurrence of sensitization in the fracture region) caused intergranular stress corrosion mechanism. Non-qualified chemical composition of the hooks (much higher carbon content than the specified of AISI 304 stainless steel) is mainly responsible for the failure of the hooks, which is a key inherent factor.