Fabrication of a polydopamine-stearic acid coating on AZ31 magnesium alloy for enhanced corrosion resistance

Purpose This paper aims to enhance the corrosion resistance of magnesium alloys, superhydrophobic surface engineering was used as an effective strategy to protect AZ31 magnesium alloy substrates. Design/methodology/approach Polydopamine was first deposited onto AZ31 magnesium alloy substrates under controlled alkaline conditions, and the surfaces were subsequently modified with stearic acid to establish superhydrophobic surface. Findings Surface characterization demonstrated excellent water repellency, with a measured contact angle of 156.3° and a sliding angle of 5.2°. FE-SEM imaging revealed micro-groove structures that account for the observed wetting behavior. The corrosion protection performance was evaluated by electrochemical impedance spectroscopy and potentiodynamic polarization in 3.5 Wt.% NaCl solution, showing that the PDA/SA samples had a corrosion current density of 1.25 × 10−6A·cm−2, which is two orders of magnitude lower than that of the bare AZ31 substrate, and a charge transfer resistance of 2.46 × 104Ω·cm². Originality/value The PDA/SA coating configuration creates a physical barrier against aggressive chloride species during exposure periods, thereby delivering corrosion protection for magnesium alloy components. The PDA/SA superhydrophobic coating offers an effective and durable strategy for corrosion protection of magnesium alloy components.