关键词: 7075铝合金, 剥蚀, 沿晶扩展, 应力腐蚀裂纹

Abstract: In order to provide an insight into the corrosion mechanisms of civil aircraft structural components, extensive investigation is performed to characterize the corrosion morphology, crack characteristics and corrosion productions of 7075-T6 aluminum alloy aircraft panel. Furthermore, the corrosion mechanisms are analyzed systematically. Microstructures and composition of coating surface on complete coating and coating corroded without peeling are analyzed respectively via scanning electron microscopy (SEM) and energy disperse spectrometer(EDS). Cross-section metallographic samples on aircraft panel are observed by optical microscope(OM), and X-ray diffraction(XRD) analysis of surface corrosion residue is also conducted. It has been found that for the surface coatings in the vicinity of rivet holes of 7075 aluminum alloy panel, bubble and cracking are easily to occur accompanied by stratiform exfoliation corrosion. Surface corrosion morphology is mainly made up of microcracks and chaps, and the major corrosion products are hydroxides. In the neighboring areas of rivet holes, a large number of discontinuous and stair-step paralleled stress corrosion cracks are induced under the surface coating. The inflation caused by crack expansion is a key factor determining surface coating desquamation. Moreover, Cl– and SO42– in corrosive solution can accelerate the atmospheric corrosion of aluminum alloy aircraft panel obviously.

Key words: 7075 aluminium alloy, Exfoliation corrosion, Intergranular expanding, Stress corrosion crack(SCC)