Efecto de las nanopartículas de ZrO 2 y L-Cys como agentes dopantes de recubrimientos sol-gel de sílice mesoporosa para la protección anticorrosiva de la aleación de magnesio AZ61

Sol-gel coatings based on GPTMS-TMOS precursor, including as dopants L-Cysteine and ZrO 2 in different concentrations, were applied on the surface of AZ61 magnesium alloy. Their corrosion resistance was studied in 0.6M NaCl solution, by immersion up to 14 days. XRD spectra revealed Mg(OH) 2 as the main corrosion product on the coated surface, while on the untreated AZ61 in addition there were several compounds of Zn with chloride. The localized corrosion attack on the untreated AZ61 was expressed by cracks and caverns, while on the dip-coated surface the corrosion was mostly through pitting. Two non-destructive electrochemical methods were employed, contrasting the electrochemical behavior of coated AZ61 with that of uncoated alloy. The tendency in the changes of the corrosion potential at open circuit correlated positively with SEM-EDS and XRD analysis. The EIS diagrams were fitted to equivalent-circuit model and the obtained corrosion resistance R corr (R s + R ct ) values strongly decreased over time. The ZrO 2 and L-Cysteine effect is influenced by the pH changes of the solution, Zeta potential surface charge, chemisorption and desorption processes, internal stress in the sol-gel precursor, as well as the change in its structure, after the encapsulation of both dopants.