Influence of rust layers on the corrosion behavior of ultra-high strength steel 300M subjected to wet-dry cyclic environment with chloride and low humidity

The influence of rust layers on the corrosion behavior of ultra-high strength steel 300M subjected to a simulated coastal atmosphere was investigated by corrosion weight loss, surface analysis techniques, and electrochemical methods. The results exhibit the presence of a large proportion of γ-FeOOH and a-FeOOH and a small amount of Fe₃O₄ in the outer rust layer. During the wet-dry cyclic process, the bonding performance and the density of outer rust layer deteriorate with the thickness of outer rust. The inner rust layer plays a main role on protectiveness, which can be attributed to the formation of an ultra-dense and adherent rust film with major constituent of a-FeOOH and a-Fe₂O₃ on the steel.