Dioctyl sulfosuccinate sodium salt (AOT) as a corrosion inhibitor for AZ31 Mg alloy: Effects of integration with layered double hydroxide (LDH)

• Investigating the corrosion inhibition of a new anionic surfactant for AZ31 Mg alloy . • Experimental and theoretical (DFT) results for corrosion inhibition of AOT. • Incorporation of AOT in LDH conversion layer on AZ31 Mg alloy. • Increased thickness and compactness of the LDH layer after modification with AOT. • Enhanced corrosion resistance of the modified LDH layer in NaCl solution. Surfactants are known for their corrosion inhibition effect for metallic substrates like magnesium (Mg) alloys. Among these surfactants, dioctyl sulfosuccinate sodium salt, also known as AOT, is noteworthy. The present study investigates the corrosion inhibition of AOT on AZ31 Mg alloy using electrochemical impedance spectroscopy (EIS). In addition, surface characterization is conducted through scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Moreover, the interaction energy between AOT and the substrate is determined using Density Functional Theory (DFT) calculations. It is observed that AOT is effective for corrosion inhibition by being adsorbed on the surface of Mg alloy. The DFT calculations yield −5.25 eV value as interaction energy confirming the EIS results and the ability of AOT to prevent corrosion. The other part of this study involves incorporating AOT in layered double hydroxide (LDH) and demonstrating the enhanced corrosion resistance of the conversion layer facilitated by the surfactant. The existence of LDH structure after immersion in AOT solution was confirmed by SEM images and XRD test. The LDH structure was enhanced by increasing LDH inner layer thickness (from 11.8 ± 0.2 µm in LDH to 16.3 ± 0.3 µm) due to the addition of AOT, resulting in improved corrosion resistance of the substrate. These findings have significant implications for utilizing AOT as a corrosion inhibitor, particularly in the context of organic coatings, where AOT can serve as a vital link between the substrate and the organic coating.