STUDY ON DETERIORATION OF THERMAL SPRAYED ALUMINUM COATING BY BRIDGE SURVEY

Abstract

Since aluminum spraying has excellent corrosion resistance, it has been applied to many steel bridges in Japan since 2000s. However, in recent years, partial degradation has been observed in steel bridges with the thermal sprayed aluminum coating. This study aims to clarify the degradation mechanism of thermal sprayed aluminum coating. This study investigates thermal sprayed aluminum coating on-site on a steel plate girder bridge. In the bridge (constructed 17 years ago at estuary) investigation, the aluminum coating is generally in good condition, but the partial degradation is concentrated inside of the girder where the corrosion environment is severe. It was also confirmed that there were many corroded parts in the lower flange weld zone. Partial degradation occurs evenly throughout the bridge, but there is a tendency for more degradation to occur on the piers, where the corrosive environment is considered to be the most severe. A large amount of salinity was detected in the results of the attached salt content measurement near the corroded parts, and it is presumed that the salt content is a major factor in promoting the deterioration of the thermal sprayed aluminum coating.