Corrosion Performance of High Strength Low Alloy Steel AISI 4135 in the Marine Splash Zone

Abstract

The corrosion behavior of high strength low alloy AISI 4135 steel was studied following extended exposure to a Qingdao field environment. When electrochemically active γ-FeOOH was formed in conjunction with easily reducible β-FeOOH, these corrosion products acted to accelerate corrosion attack in the marine splash zone (i.e., steel structure above the water line that is splashed by sea spray). It had also been observed that the pH beneath the rust layer exhibited a minimum during the non-splash part of wet and non-splash corrosion cycling. These acidic conditions contributed significantly to an increase in the rate of localized corrosion, both beneath the rust deposits and within rust cracks and voids within pockets of rust deposits over the steel surface.