Corrosion Analysis on Wrap Nut and Flat Mouthpiece of Galvanized Passivation 45A Steel

Phenomenons of zinc coating surface color darkening and locally appearing grayish white corrosion products, were found on the surface of the galvanized passivation 45A steel wrap nut and flat mouthpiece after assembly and use for some time. Through macroscopic and microscopic morphology analysis, energy spectrum analysis, metallographic examination, combined with assembly and test process analysis of the parts, it is confirmed that the surface corrosion of the parts was caused by the uncleaning of the soap liquid in the airtight test. Further simulation test results show that the corrosion degree of the surface of the part was positively correlated with the residual time and concentration of the soap liquid, and the high heat and high humidity environment promoted the corrosion.