Corrosion Behaviors of Mo-containing Low Alloy Steels Exposed in Simulated Acidic Marine Atmosphere Environment

The periodic immersion corrosion experiment was adopted to simulate the acidic marine atmosphere environment. The corrosion behavior and corrosion resistance mechanism of Mo-containing low alloy steels were analyzed by weight loss experiment, electrochemical experiment, scanning electron microscopy, energy disperse spectroscopy and X-ray diffraction spectroscopy. The results showed that the microstructures of low alloy steels with Mo mass fraction of 0.2%, 0.4%, 0.6%, 0.8% and 1.0% were composed of ferrite and pearlite. In the early stage of corrosion, the corrosion products of low alloy steels did not show obvious delamination when Mo content was 0.2%~0.8%, and all samples showed obvious delamination in the middle and late corrosion periods. The rust layer became thicker with the increase of immersion time, and when Mo content was 0.4%, the inner rust layer could provide better protection with relatively denser layer and smaller cracks to the substrate. The corrosion rates of the 5 low alloy steels increased first and then decreased with the increase of immersion time. When Mo content was between 0.2% to 0.4%, it could improve the corrosion resistance performance, while when Mo content was beween 0.6% to 1.0%, it had a small influence on enhancing the corrosion resistance, which was consistent with the results of rust layer analysis and weight loss test.