Abstract Variations in the state of electric contact surface with make–break cycles were investigated with Pd-plated contact in an organic gas/air atmosphere including benzene, C 6H 6, cyclohexane, C 6H 12, or n-hexane, C 6H 14. By introducing the organic vapor into an ambient atmosphere, contact resistance increase was suppressed. Quantitative analysis of the fretted surface was performed by electron probe X-ray microanalyser (EPMA), and it was found that C and O exist on the surface in an atomic ratio of 7.1 for benzene, 6.2 for cyclohexane and of 5.9 for n-hexane, respectively, suggesting the generation of definite reaction products. Analytical results using Fourier transformed infrared absorption spectroscopy (FT-IR) showed that the products included carbonyl or carboxylic groups. The wear rate of the contact surface and film thickness of the reaction product were discussed in relation to the tribochemical reaction.