The corrosion inhibition of C38 steel in molar HCl by N,N-bis[2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl]buthylamine (P1) and 5-{N,N-bis[2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl] amino} pentanol (P2) has been investigated at 308 K using electrochemical and weight loss measurements. Measurements show that these compounds act as good inhibitors without changing the mechanism of the corrosion process. Moreover, the inhibiting efficiency increases with the increase in concentration of the studied inhibitors. Compound P2 showed better protection properties even at relatively higher temperatures when compared to P1. The associated activation corrosion and free adsorption energies have been determined. P1 and P2 are adsorbed on the C38 steel surface according to a Langmuir isotherm adsorption model.
The effect of two pyridin-pyrazol derivatives, N-[(3,5-dimethyl-1H-pyrazol)methyl]pyridine-2-amine (TB5) and 5-bromo-N-[(3,5-dimethyl-1H-pyrazol)methyl]pyridine-2-amine (TB6), newly synthesized, on the corrosion of mild steel in 1.0 M HCl was investigated by weight-loss and various electrochemical techniques. Results obtained reveal that these pyridin-pyrazol derivatives perform excellently as corrosion inhibitors for mild steel in hydrochloric solution. Polarization curves showed that both TB5 and TB6 are mixed-type inhibitors in acidic medium. A kinetic study of steel in uninhibited and inhibited acid for TB6 was also achieved to provide suitable investigations on corrosion inhibition mechanism in 1.0 M HCl solution. The effect of concentration and temperature on the inhibiting efficiency has been examined. The thermodynamic parameters for both dissolution and adsorption processes were calculated and discussed for TB6. The adsorption of inhibitor TB6 on the mild steel surface obeys the Langmuir adsorption isotherm equation.
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