［Objective］In response to the increasingly prominent corrosion issue at door hemming positions，this study focuses on the frequent filiform corrosion failures of zinc-aluminum-magnesiumcoated steel sheets at the hemming of door inner panels. It aims to systematically evaluate the corrosionresistance of the coated steel sheets，clarify the induction mechanism of filiform corrosion，and propose efficient prevention and control technical schemes.［Methods］ Systematic corrosion resistance assessment of zinc-aluminum-magnesium coated steel sheets was conducted from three core dimensions：uniform corrosion，sharp-edge corrosion，and crevice corrosion. Combined with actual service conditions，the structural characteristics of the hemming，material surface state，and environmental factors were analyzed emphatically to explore the formation path of filiform corrosion in depth.［Results］ There exists an electrochemical potential difference in the zinc-aluminum-magnesium coating. Combined with the structural defect of insufficiently filled hemming adhesive at the door hemming and poor quality of the pretreatment film，acetic acid medium remains in the hemming cavity. These three factors act synergistically in a high-temperature and high-humidity environment，ultimately triggering filiform corrosion. The adoption of combined protective measures such as full-cavity adhesive sealing，improving the quality of the pretreatment film，removing residual acetic acid，and spraying anti-corrosion wax can significantly reduce the incidence of this corrosion problem.［Conclusion］The corrosion resistance of zinc-aluminum-magnesium coated steel sheets should bedefined through multi-dimensional comprehensive evaluation. The filiform corrosion at the hemming ofdoor inner panels is the result of the combined action of electrochemical potential difference，hemming adhesive filling defects，pretreatment film quality，medium residue，and environmental factors. The application of targeted combined protective technologies can effectively improve the corrosion reliabilityand service life of this key position.
