Rapid Synthesis and Evaluation of a Cheaper Corrosion Inhibitor for Steel in HCl Solution

A corrosion inhibitor suitable for industrial production and field application was rapidly synthesized from benzene-1,2-diamine, benzaldehyde, methanol, hydrochloric acid, and FeCl3. The mechanism of corrosion and its inhibition was proposed. We investigated the effect of the main reactants on corrosion rate, and optimal synthetic composition (benzene-1,2-diamine 10 g, benzaldehyde 10 g and ferric chloride hexahydrate 8 g) of the inhibitor was determined by using an orthogonal experimental design. The corrosion inhibition performances for N80 and Q235 steel in acid medium and oilfield water-injection were studied by employing the weight loss method. The inhibition efficiency for N80 steel reached to 99.24% in 15 wt.% HCl solution for 4 hours at 90 °Cat the dosage of 1.2 wt.%, while in the water-injection, the efficiency for Q235 steel was 82.4% at 50 °C for 7 days at the concentration of 30 mg/L. Corrosion rates in acid medium and water-injection showed that the inhibitor has good corrosion inhibitive behavior for the steel surface and the inhibition efficiency increased with increasing concentration. Three kinds of compounds with synergistic corrosion inhibition were introduced to study, and ammonium bromide exhibited the best synergy. Attempts were made to fit the test values to different isotherms, it was found that the adsorption of the inhibitor on Q235 steel surface obeys Langmuir adsorption isotherm. The calculated value indicated that the adsorption reaction could spontaneously occur andthe inhibitor molecules could be well adsorbed on Q235 steel surface in oilfield water-injection at 50 °C.