Analysis of Corrosion Failure of the Positioning Sleeve of a Limit Positioner

Corrosion failure was investigated in the aluminum alloy positioning sleeve of a limit positioner used on a coastal railway line. Field inspection, optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and bulk chemical composition analysis were used to characterize the failed component. The sleeve exhibited layered exfoliation at the surface and blocky spalling in the central corroded region. Microscopic observations revealed intergranular cracking and separation of corrosion layers. Sulfur was detected in the analyzed regions, whereas chlorine was detected in one region. The measured Cu content was 2.08 wt%, exceeding the 0.10 wt% upper limit specified for 6082 aluminum alloy in GB/T 3190–2008. These findings suggest that the failure was associated with the coastal corrosive environment and the nonconforming alloy composition. Pitting, intergranular corrosion, and exfoliation were identified as relevant forms of damage, with sea breeze and train-induced airflow potentially promoting the detachment of loosened material. Material composition control, routine inspection, and suitable surface protection are recommended to reduce similar failures in catenary components.