Experimental And Theoretical Investigation Of The Adsorption Behaviour Of Novel Triazole Compounds As Inhibitors

The use of inhibitors is one of the most practical methods for protection against corrosion. Numerous researches on corrosion inhibition using organic compounds have been reported due to its highly efficient and cost-effective. It has been accepted that most organic compounds employed as corrosion inhibitors can adsorb on the metal surface through heteroatoms such as nitrogen, sulfur, oxygen, phosphorus and multiple bonds etc preventing steel from corrosion. Based on the conclusions, various triazole-type compounds have been used as organic inhibitors in acidic media. However, the corrosion inhibiting mechanism of the triazole-type compounds is not so clear. The aim of this work is to obtain a better understanding of the inhibiting behaviour of the triazole derivatives and predict corrosion efficiency of similar structures in order to design compounds for testing their corrosion inhibition.The three series including eleven kinds of novel triazole compounds involved in this paper, which with non-toxicity and environmentally friendly. The inhibiting performance of these derivatives was evaluated by weight loss, electrochemical test, scanning electronic microscope (SEM), and quantum chemical calculations. The corrosion inhibiting mechanism of these derivatives and the relationship between the molecular structure and their inhibiting efficiency were discussed. Some results were drawn as follows:The oxime ether-triazole derivatives shown excellent inhibition properties for the corrosion of mild steel in 1 M HCl solutions, and the inhibition efficiency increases with increasing the concentration of the inhibitors; The inhibition ability of these compounds is follows in the order of 2,5DATM≈3,4DATM > CATM > MATM≈FATM, and the inhibitor efficiencies determined by polarization, EIS, and Weight loss methods are in good agreement. The adsorption model obeys the Langmuir adsorption isotherm at 298K, and the negative values of free energy of adsorption indicated that the adsorption of the inhibitors is a spontaneous process.The S-triazole-triazole derivatives were investigated as corrosion inhibitors of mild steel in 0.5 M H2SO4, an exception is at a low concentration, the inhibitors PMTT and NMTT, which acts as a stimulator. The inhibition efficiency increases with the inhibitor concentration. The inhibitor molecule exhibits cathodic inhibition performance via adsorption on the steel surface blocking active sites. Potentiodynamic polarization measurements show that the 2-H-pyrazole-triazole derivatives are the mixed-type inhibitors, and addition of inhibitors causes a decrease in the corrosion current. EIS measurements also indicated that the presence of inhibitors raises the charge transfer resistance, it shows that inhibitive abilities of inhibitors depends on the adsorption of molecule on metal surface. The negative values of indicated that the adsorption of these triazole molecules is a spontaneous process, and both chemisorption and physisorption might take place on the mild steel surface.Quantum chemical calculation was theoretically provided the absorption sites of these Triazole molecules. Based on the research of the quantitative structure-activity Relationship (QSAR) of these inhibitors, the possible mode of inhibition equations were presumed. It is useful to provide some valuable information to synthetic new corrosion inhibitors.