Addressing the fracture failure of locking pins used in suspension insulators on a transmission line in Ningxia

this study employs macroscopic examination

chemical composition analysis

metallographic testing

scanning electron microscope（SEM）

and energy dispersive spectrometer（EDS） for investigation.It was observed that the locking pin

made of H62 brass

was enveloped with an uneven layer of pure copper

which had a clear interface with the brass.The cracking initiated at thicker areas of the copper coating and expanded along the grain boundaries

with sulfur elements present in the fracture.Through a comprehensive analysis

it is concluded that the locking pin experienced dezincification corrosion

primarily driven by the surface dissolution-reprecipitation mechanism

which consequently weakened its mechanical properties.Under stress during operation

micro-cracks formed on the dezincified surface and expanded through stress corrosion

resulting in the locking pin’s fracture failure.