Inhibiting Properties of Some Heterocyclic Amide Derivatives as Potential Nontoxic Corrosion Inhibitors for Carbon Steel in 1.0 M Sulfuric Acid

Three compounds based on heterocyclic amides were synthesized, purified, characterized, and evaluated as corrosion inhibitors for carbon steel in 1.0 M H2SO4 solution using various techniques such as the weight loss, hydrogen evolution, thermometric, and potentiodynamic polarization. Effects of raising the concentration (50, 100, 150, 200 ppm) of amide compounds and temperatures were analyzed. The percentage inhibition efficiency went up with increasing inhibitor concentrations but decreased with temperature. Thermodynamic activation parameters were computed and discussed. It was found that the heterocyclic amide compounds reduce the weight loss, the amount of hydrogen evolved, the corrosion current density; thus the inhibition efficiency increases indicating the inhibiting power of these compounds. The maximum corrosion inhibition efficiency obtained by using 200 ppm from compound 3 is 95%. The potentiodynamic polarization curves proved that amide compounds act as inhibitors of a mixed type. The inhibition action of the three compounds was due to blocking the surface of the electrode by adsorption the inhibitor molecules according to the Langmuir isotherm. The data obtained via different techniques are in good agreement with each other and illustrate that the prepared amides can be considered to be potential nontoxic corrosion inhibitors.