ABSTRACT Different theoretical, electrochemical and surface techniques were applied to study the corrosion inhibition effects of 2-Amino-6-hydroxybenzothiazole in 5% HCl solution. The density functional theory was carried out and quantum chemical factors like the energy gap, energy of highest occupied molecular orbital, the energy of lowest unoccupied molecular orbital, the fraction of electron transferred, and Mulliken charges have been calculated. In addition, according to quantum calculation, S atom in 2-Amino-6-hydroxybenzothiazole indicated more tendency for electrophilic attack in adsorption. The main reason for high inhibition efficiencies in very low concentrations is the planar and simplicity of inhibitor structure which leads to increasing the efficiency of adsorption by functional group especially sulfur. Electrochemical frequency modulation and potentiodynamic polarization indicated that this material has excellent inhibiting features in very low concentrations. The influence of DC trend on the explanation of electrochemical noise data was evaluated by polynomial fitting and the optimum polynomial order m=4 was obtained. Noise resistance and the inhibition efficiency was calculated and compared in different methods. The theory of shot noise in frequency domain was used to obtain the electrochemical event charge. The corroded surface of steel in the absence and existence of thiazole compound was studied by Atomic force microscopy.

Adsorption isotherm of N,N'-bis(2,4,6-trihydroxyacetophenone)-2,2-dimethylpropandiimine (THAPDP) as an environmentally friendly Salen Ligand corrosion inhibitor on mild steel was studied in alkaline solution (pH=10) containing 3% NaCl. Measurements were carried out using electrochemical and surface techniques. Potentiodynamic polarization curves suggested that this compound was an effective corrosion inhibitor for mild steel and the protection efficiency was increased with the increase in inhibitor concentration. The experimental results indicated that this organic compound was a mixed-type inhibitor. Adsorption on the mild steel surface followed the Langmuir isotherm model. Activation parameters and thermodynamic adsorption parameters of the corrosion process such as Ea, ΔH, ΔS, Kads, and AG . were calculated at different temperatures.

The effect of changes in grain size on corrosion resistance of the pure tough pitch copper stripwas investigated in acidic and alkaline NaCl solutions. Accumulative roll bonding as sever plastic process was applied up to 8 cycles to produce the ultrafine graincopper. Polarization and electrochemical impedance tests were used for corrosion resistance investigations. Corrosion morphologies were analyzed by FE-SEM. Results showed that the corrosion resistance decreased up to cycle 2 and increased after rolled for the fourth time due to UFG grain formation after cycle 4. The corrosion degradation in cycle 8 was uniformand it was more intergranular for the sample of cycle 2 and the unrolled counterpart.