Steel suspension systems of contact line can not be used for long (over 60 years) in corrosive environments under the current maintenance system. To extend their service life, we have developed corrosion protection coating systems. We conducted field tests with the developed coating systems, which mainly consist of high build epoxy paints, as coating films shall be sufficiently thick as the essential performance. The test result proved that the systems are durable when the film thickness is larger than 120 u m on degraded galvanized steel surfaces.