Passivation of corrosion product layer on AM50 Mg by corrosion inhibitor

The influence of sodium dodecyl sulfate (SDS) on morphology and chemical composition of corrosion product layer formed on α-Mg matrix and cathodic Al-Mn intermetallic was systematically investigated by using FIB and TEM analysis for the first time to disclose the underlying inhibition mechanism. A porous corrosion bi-layer composed of crystalline MgO and Mg(OH)₂ was observed on both of α-Mg and Al-Mn intermetallic. It was found that a passive inner layer was deposited on α-Mg after immersion in SDS-containing NaCl solution, which can be ascribed to steady-state growth of magnesium and aluminum oxide under the protection of hydrophobic group of SDS. The inhibition mechanism of the inhibitor was mainly associated with formation of dense oxide layer on α-Mg matrix and preferential adsorption of SDS on the corrosion layer deposited on Al-Mn intermetallic.