Effect of deposition of Al/AlN coating on medium-Mn steel on its corrosion resistance in 5 wt.% NaCl

Medium-Mn steel has wide use in marine structures because of its low alloy cost, high strength, and high toughness. However, it has poor corrosion resistance in the marine atmosphere. In this paper, Al/AlN double-layer coating was fabricated on medium-Mn steel to improve its corrosion resistance. An Al/AlN double-layer was deposited on the surface of medium-Mn steel by direct current magnetron sputtering. The effect of Al/AlN film deposition on the corrosion behavior of medium-Mn steel was investigated by X-ray diffraction, scanning electron microscopy, and electrochemistry. The corrosion environment is the marine atmosphere, which is simulated using the neutral salt spray test. The results showed that AlN and Al can provide excellent protection against corrosion for medium-Mn steel. Medium-Mn steel coated with Al/AlN double films has high rust layer density after corrosion, and the corrosion products contain more anti-corrosion phase α-FeOOH. The deposition of Al/AlN thin films can restrain the formation of Mn x O y . The corrosion current density decreases from 2.389×10 ⁻4 to 3.718×10 ⁻5 A·cm ⁻2 . The deposition of Al/AlN double-layer films can effectively improve the corrosion resistance of medium-Mn steel in the marine atmosphere.