Experimental and theoretical study of adsorption of L-cysteine on the passivation and corrosion inhibition of aluminum alloy in alkaline environment

<p class="Default">L-Cysteine (L-Cyst) was tested as a corrosion inhibitor of 3003 aluminum alloy (AA3003) in Na₂CO₃ 0.1M + NaCl 1M solution. The inhibition action of this inhibitor was studied by using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and cyclic voltammetry (CV) techniques. The temperature effect on the inhibition efficiency was studied in the range from 298 to 328K, and the values of activation thermodynamic parameters were calculated and explained. Experiment results show that inhibition efficiency increases with the increase of L-Cysteine concentration, and its inhibition efficiency reaches 92% at 10⁻³M. The inhibition efficiency decreases slightly with the elevation of a corrosive medium temperature. Analysis of the polarization curves revealed that L-Cyst is considered a mixed inhibitor. The results from electrochemical measurements and theoretical calculations are in good agreement. The morphological changes of the surface during corrosion, in the presence and absence of the inhibitor, were studied by scanning electron microscopy (SEM).</p>