Corrosion Causes of Self-Locking Nuts of a General Aircraft

In the periodic inspection of a type of general aircraft, it was found that the self-locking nuts of the fixed brake torsion plate were seriously corroded, and a small number of nuts were completely broken, resulting in the loosening of the bolts connected to them. According to the statistical analysis of the nut status of the same type of aircraft in five airport operating environments, 10 samples were selected for research. The macro and micro morphology of the corroded nuts were observed by 3D optical microscope and scanning electron microscope (SEM). The elements of the outer surface and the fracture cross section of the nuts were compared by energy dispersive spectrometer (EDS). According to the coating characteristics and operating environment, the causes of corrosion of this type of nuts were analyzed. The results showed that the harsh external environment, actual operating conditions and personnel operation mode caused the damage of the coating on the nut surface. The damage of the coating was the main reason for the corrosion of the nut in the brake area. The acid rain and humid environment aggravated the corrosion of the nut. The damage and long-term corrosion of the coating caused a large thickness loss rate of the nut.