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The aim of this article is to study the contact surface morphology and the corrosion state of sealed relays and analyze the correlation relationship of contact spot corrosion types under different deformation variables. In this article, a contact planar‐layered model of contact pairs was established, the contact corrosion status of each level was explored, and the corrosion distribution at different contact points of the contact group was obtained. In this article, combined with the dynamic contact process analysis and corresponding to the contact position of the contact group, the contact difference plane was proposed to characterize the contact state of the contact group. The genetic algorithm to optimize the maximum‐entropy double threshold method (Genetic‐KSW) was used to calculate the mutative segmentation threshold, to layer the contact difference plane, and to solve the problem of threshold fluctuation caused by big data. Finally, the corrosion product type and the corrosion distribution corresponding to different corrosion morphologies at each level of the contact group were analyzed from the angle of the corrosion film. The conclusion is that the first contacted level I region is obtained as a mild corrosion region that generates oxidative corrosion and mild wear, and the level II region is a complex compound containing N/C/S/P. The pit corrosion area is shallow, and the contaminant products Na2CO3 and NaNO2 are widely distributed on the edge of the corrosion pit with scattered spots. In contact with the level III area, the deep corrosion pits and the shallow pits coexist, and the corrosion product is the heavily corroded area of AgCl. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]