In situ surface film evolution during Mg aqueous corrosion in presence of selected carboxylates

•Carboxylates modify kinetics of Mg(OH)2 film growth on Mg during aqueous corrosion.•Mg(OH)2 nano-crystals formed in inhibitors solutions limit Cl− access to Mg surface.•Salicylate adsorbs chemically on Mg(OH)2, dissolves Fe-containing inclusions.•2,5-pyridinedicarboxylate precipitates in the form of coordination polymer.•Inhibition by fumarate seems to be due to adsorption via carboxylate group. Mechanisms of inhibition of Mg aqueous corrosion in presence of chloride by sodium salicylate (Sal), 2,5-pyridinedicarboxylate (PDC) and fumarate (Fum) were studied by in situ Raman spectroscopy, ATR-FTIR, GD-OES and hydrogen collection. In situ detected surface films were composed by Mg(OH)2 nano-crystals and included inhibitors. All carboxylates significantly modified Mg(OH)2 growth kinetics as well as pevented chloride incorporation in the film. Vibrational spectra of the surface films demonstrated specific interactions between the carboxylates and the surface: adsorption of Sal and Fum on the oxide/hydroxide, precipitation of coordination polymer by PDC, dissolution of iron inclusions via formation of iron-Sal soluble complexes.