No abstract

No abstract

a b s t r a c tThe effect of addition of gramine on mild steel dissolution in deaerated 1.0 M hydrochloric acid was studied through potentiodynamic polarisation curves, electrochemical impedance spectroscopy and gravimetric measurements in the temperature range from 25°C to 55°C. Gramine was found to shift the corrosion potentials towards less noble values and decrease both dissolution of mild steel and hydrogen evolution reaction. Gramine did not affect the corrosion reaction mechanism (blocking effect). Results obtained from the several measurement techniques were in good agreement and revealed good inhibition efficiencies in the concentration range (0.75 mM Ä 7.5 mM) particularly at higher concentrations.

The inhibiting action of indole-2-carboxylic acid (C 9 H 7 NO 2 ) on the corrosion of commercial copper in aerated 0.5 M sulfuric acid (H 2 SO 4 ) has been investigated in the temperature range from 25°C to 55°C by weight loss, potentiodynamic and analytical tests, and the determination of double-layer capacitance. The results have revealed a good inhibitor effi ciency, up to 98% in the concentration range from 1 × 10 -4 M to 4 × 10 -3 M. Indole-2-carboxylic acid has been found to act as a mixed inhibitor. The kinetics of Cu + and Cu 2+ formation that followed in 72 h of gravimetric testing shows that indole-2carboxylic acid probably affects the corrosion reaction mechanism through complexes with cuprous ions. The corrosion rates determined through weight-loss measurements are much higher than those obtained with potentiodynamic tests. This is in accord with other researchers who have found limitations to the extrapolation of polarization curves (and to the theory of mixed potentials) in the determination of corrosion rates. The adsorptive behavior of indole-2-carboxylic acid also has been investigated in a wide potential range (-900 mV to 200 mV with regard to corrosion potential [E corr ]).

No abstract