Inhibition of AZ31 Mg alloy corrosion by anionic surfactants

Gravimetric and electrochemical measurements were applied to study the inhibiting action exerted by some anionic surfactants (sodium salt of N-lauroylsarcosine, N-lauroyl-N-methyltaurine, dodecylbenzensulphonic acid or sodium lauryl sulphate) towards AZ31 Mg alloy corrosion in electrolyte solutions. The influence of the additive concentration, immersion time and type of surfactant was evaluated.Their inhibiting effects was attributed to a rapid adsorption on the metallic surface, which limited the cathodic reaction, followed by a precipitation stage with Mg++ ions that made the inhibiting layer thicker and less defective, so that, over time, the anodic oxidation was almost blocked in a wide potential interval.

► The effects of anionic surfactant on AZ31 Mg alloy corrosion inhibition is studied. ► The influence exerted towards the anodic and cathodic processes is evaluated. ► An interpretation of inhibition mechanism is proposed. ► The influence of a precipitated layer on the anodic Mg oxidation is determined.