DURABILITY OF STEEL BRIDGE COATING SYSTEMS CONSIDERING ACID RAIN

摘要

Paint and metallic coating systems have been widely used to prevent corrosion on steel bridges in corrosive environments. Many research efforts have been made to understand the influence of acid rain on durability of materials; however, but how the acid rain is going to affect durability of the steel bridge coating systems has not been examined yet. This study performed an accelerated exposure test using acid rain spray combined cycles during 100, 200 and 300 days. The accelerated exposure test is based on the S6-cycle specified in Japanese Industrial Standard (JIS) K 5621, but replacing the salt water spray period with the acid rain spray period. The test specimens were coated with three types of paint systems including A, I and C-paint system used in Japan, and four types of metallic coating systems including zinc hot-dip galvanizing, zinc-aluminum alloys spraying, zinc-aluminum pseudo-alloys spraying and aluminum spraying. After the accelerated test, the specimens were measured for gloss, adhesive strength, blistering area, and so on for the paint systems, and reduction of the coating thickness and reduction of the coating area for the metallic coating systems. It is found from this study that the blistering area of A-paint system resulting from the acid rain spray combined cyclic corrosion test was remarkably larger than that from the salt water spray combined cyclic corrosion test. As for the metallic coating systems, the acid rain reduces durability of corrosion resistance of zinc hot-dip galvanizing, zinc-aluminum alloys and aluminum spraying.