New Test Solution for Cyclic Corrosion Test Reproducing Atmospheric Corrosion Behaviors of Steel and Zinc in Coastal Area

Accelerated corrosion tests need to ensure compatibility between acceleration of corrosion and reproduction of atmospheric corrosion in actual coastal environments. However, gordaite, a highly protective zinc-corrosion product, is not produced in cyclic corrosion tests using general NaCl aqueous solutions. Moreover, the ratio of the corrosion rates of steel/zinc after those tests is too small compared to that after outdoor exposure. Conversely, when artificial seawater is used, the corrosion products contain too much gordaite, and the ratio of corrosion rate of steel/zinc is too large compared with that for outdoor exposure. With these solutions, the corrosion resistance of zinc is underestimated or overestimated. Therefore, we developed a new test solution for reproducing the atmospheric corrosion behavior of zinc in coastal area. The solution enables us to evaluate corrosion resistance of zinc-rich paint and galvanized steel in coastal areas more accurately than other solutions do.