As an example of structure-efficiency relationship study, this paper aims to evaluate the corrosion inhibition effect of two cationic surfactants, cetyl-trimethyl ammonium chloride (CTAC) and cetyl-dimethyl-hydroxyethyl ammonium chloride (CDHAC), and to discuss the effect of structure on the performance by thermodynamics methods.
The effect of the two cationic surfactants, CTAC and CDHAC, on the corrosion of the mild steel in HCl solution was investigated by using weight loss measurements, and the activation energies of CTAC and CDHAC involved in the corrosion inhibition were calculated and discussed.
The weight loss measurements showed that the corrosion inhibition efficiency of CDHAC was higher than that of CTAC in any case. The effects of the structure on performance were discussed, and the following data are available from the results, all of ΔS are positive, the values of ΔG are both close to −40 kJ·mol-1 and the values of ΔH are 10.960 and 36.996 kJ·mol-1, which indicate that the surfactant molecules are spontaneously adsorbed on the surface of the steel surface, and the adsorption on the steel plate is endothermic chemical adsorption.
The available data show that most organic inhibitors undergo physisorption on the metal surface, while in the presence of non-bonded and p-electrons, the inhibitor molecules may undergo chemisorption. This work showed that the two surfactant molecules are spontaneously adsorbed on the surface of the steel surface, and the adsorption on the steel plate is endothermic chemical adsorption.
