COMPARISON OF ADHESION AND HARDNESS OF FREQUENTLY REPAINTED STEEL RAILWAY BRIDGE COATINGS OVER MULTIPLE PERIODS

Abstract

 In Japan, the general practice for repainting steel railway bridges is to remove deteriorated coatings and repaint while leaving the active coating. For this reason, in steel railway bridges that have been in service for a long time, the coating thickness increases, and internal stress increases. In addition, the coating hardens and becomes brittle over time, which may cause cracks and peeling. However, there are few cases where the adhesion and hardness of coatings have been compared over multiple periods. Therefore, we conducted appearance surveys, coating history surveys, and adhesion evaluation tests on actual bridges over two periods on steel railway bridges that were in service in the 1960s and have been repainted frequently, and measured the indentation hardness of each coating layer in laboratory tests. As a result, although slight coating cracks were confirmed, most of the coatings had sufficient adhesion, and no peeling of the coating was confirmed over a large area. On the other hand, we found that the adhesion of the coatings was declining, and the red lead rust prevention paint in the bottom layer was hardening.