In the Airport Railroad, the Yeongjong Bridge has a length of 4,420 m and connects Yeongjong Island with the mainland of Incheon City. The bridge is a two-level structure, consisting of a six-lane road at the upper level and a combination of a road and railroad at the lower level. The environmental conditions for the electric railway come mainly from the salt injury area and a heavy industry zone, and the maintenance cycles are determined differently depending on these conditions. This study analyzed the deterioration characteristics of long rod insulators produced with a movable ceramic bracket and polymer materials in the Yeongjong Bridge section of the Airport Railway operating in the salt injury area according to the material characteristics. Comparison of the corona measurements when the insulators were cleaned at the same time showed that the polymer insulator had a higher insulation performance than the ceramic insulator.