Investigation of physicochemical properties of guanidine-based corrosion inhibitor

Physico-chemical analyzes were used to investigate the anti-corrosion potential of guanidine thiocyanate derivatives for steel in 2.5 M HCl-HF solution in the temperature range of 70-90°C. The obtained results proved that the inhibition efficiency increases with the increase of inhibitor concentration from 1.1•10-4 M to 9.8•10-4 M. The degree of protection at the minimum concentration of the inhibitor in the HCl-HF solution at 70°C was 92.1%. The values of Gibb’s energy (ΔGoadsor.) for the process ranged from -18.78 kJ/mol to -28.63 kJ/mol. This result indicates the spontaneous adsorption of inhibitors on the steel surface, and the adsorption mechanism is chemisorption. Analyzing the values of enthalpy (ΔH°), it was found that the adsorption of the inhibitor on the steel surface was endothermic. The entropy value of chemosorption means that this process occurs with a decrease in entropy.

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