SURFACE-ACTIVE SUBSTANCES AS INHIBITORS OF LOCALIZED CORROSION OF THE ALUMINUM-ALLOY AA-6351

Some surface-active substances were tested as corrosion inhibitors of the aluminium alloy AA 6351 in 0.01 M NaCl under both free corrosion conditions and anodic polarization. The substances used were sodium salts of N-dodecanoyl-N-methylglycine (NLS), dodecylsulphate (LS), N-dodecanoyl-N-methyltaurine (NLT) and dodecylbenzensulphonate (DBS). The tests performed to measure the efficiencies of these substances and to study their inhibition mechanism (gravimetric measurements, electron probe micro-analysis, potentiodynamic, potentiostatic and galvanostatic tests and electrochemical impedance spectroscopy) suggest that these substances act by adsorption on the aluminium surface oxide and displacement of adsorbed chloride ions. An attempt was made to explain the marked inhibiting properties shown by NLS.