Electrochemical, DFT and Mont Carlo Simulations Studies to Evaluate the Inhibition Effect of Novel Pyridazine Derivatives on Iron Pitting Corrosion in 3.5 % NaCl

摘要

(6-Phenyl-pyridazin-3-ylsulfanyl)-acetic acid ethyl ester (PPS-A) and 4-(6-Phenyl-pyridazin-3-ylsulfanyl)-butyric acid ethyl ester (PPS-B) are synthesized and characterized as novel S-alkylatedpyridazine derivatives with different side chain lengths. The effect of S-alkylated side chain lengths inPPS-A and PPS-B is investigated for their protective mechanism towards iron pitting corrosion in 3.5% NaCl and compared to their parent pyridazine (PPS) using electrochemical measurements andtheoretical calculations. It is found that, the studied pyridazine derivatives shift both the corrosionpotential and the pitting potential of iron to more noble values. Furthermore, the mechanism of theinhibition is correlated to the presence of the S-alkylated side chain in PPS-A and PPS-B compared toPPS, as well as to its different lengths between PPS-A and PPS-B. Moreover, the structure ofFe/electrolyte interface in case of PPS-B behaves as more ideal capacitive rather than that in case ofPPS-A, due to the adsorption of insulating barrier layers on Fe/electrolyte interface. The best fitadsorption isotherm is found to be Langmuir adsorption isotherm with physical nature. DFTcalculations show that, the charge density around the adsorption active sites increase as the S-alkylatedside chain became more length. The adsorption behaviour of the studied pyridazine derivatives issimulated using Mont Carlo molecular dynamics that agree well with the experimental data.