Unveiling the synergistic corrosion inhibition mechanism of carboxylate inhibitors for magnesium

The synergistic corrosion inhibition mechanism of sodium salicylate (SAL) and succinic acid (SA) on the pure Mg is investigated at the molecular level. High inhibition efficiency of 90.6% is achieved in a NaCl solution containing 5 mM SAL and 50 mM SA. SAL exhibits a higher affinity than SA for reacting with hydroxide/oxide and adsorbing onto the Mg surface, thus playing a dominant role in enhancing the corrosion performance. Furthermore, SAL facilitates the adsorption of SA due to the strong hydrogen bond formed by the -OH on the benzene ring of SAL and the -COO - of SA, thus promoting the formation of a thin, oxide-rich and hydrophobic surface layer. For the first time, the composition and inner-to-outer distribution of the surface layer (including MgO, Mg(OH) 2 , MgO 2 COOH - , MgCO 3 , COOH - , and adsorbed SAL or SA ions) are elucidated.