Corrosion degradation of metallic coating systems for steel bridges

This study examined to evaluate corrosion durability of metallic coatings system for steel bridges. Accelerated corrosion cyclic tests conforming to JIS K5621 were carried out on four types of metallic coating systems, Zinc hot-dip plating and three thermal sprayings of Zinc and/or Aluminum. After metalic coating, cross-scribed lines reaching the steel substrate were mechanically made in the coated surface, and uncoated region of 20 × 70mm were also introduced in the specimens. The coated test specimens were exposed into the S6-cycle corrosion environments for 300 days(S6-1200 cycles). The surface geometry and thickness of the metal coating layers were measured at the exposure times of 0,100,200, and 300 days. After the measurements, corrosion productions on the test specimens were removed mechanically and chemically, and then surface geometry and thickness loss were also measured. From the test results, the corrosion degradation of the four types of metalic coating systems was evaluated.