EVALUATION OF LONG-TERM DURABILITY OF THE NEW LONG-TERM DURABLE COATING SYSTEM APPLIED TO REPAINT AN EXISTING STEEL BRIDGES

Abstract

 The Guidelines for the Design and Construction of Steel Structure Paintings were revised in August 2025, adding a new long-term durability coating system, SiE. This coating system offers corrosion protection comparable to conventional long-term durability coating systems, but its use on actual bridges has been limited, making it necessary to confirm the effects of aging degradation from the perspective of long-term durability. Therefore, we applied the SiE coating system to samples cut out from actual bridges, for each surface preparation method, and conducted a 60-year thermal aging test to examine the appearance and adhesion of the coating. When the previous coating was completely removed, it was found that no cracking was observed and the adhesion was sufficient. Furthermore, the wear rate of the topcoat coating was estimated based on the results of a 3-year outdoor exposure test. This indicated a wear rate of 1.1 μm/year, and the durability was estimated to be approximately 34 years for the standard coating thickness. The results of the two tests indicated that, in general environments with little impact from salt, it is possible to repainting cycle of more than 30 years