New monoamine and diamine compounds were synthesized from dodecylamine and 1, 12-dodacanediamine, and evaluated as acid corrosion inhibitors for low-carbon steel. The inhibition behavior of these compounds was examined using gravimetric and electrochemical methods (linear polarization and Tafel plot). Weight loss tests were conducted in 1M HCl at 140°F for six hours. To simulate acid stimulation treatments, other weight loss tests were conducted using typical acid stimulation concentrations 4.1 and 7.7 M HCl, (equivalent to 15 and 28 wt%, respectively) at 140°F for two hours. The effects of corrosion inhibitor type and concentration, and acid concentration were investigated.

Experimental results indicated that examined monoamine compounds exhibited better corrosion inhibition for low-carbon steel in 1 M HCl acid solution than their corresponding diamine compounds. This behavior was clearly observed at a low corrosion inhibitor concentration of 50 ppm. Tafel Plot results suggest that the inhibition mechanism for all examined compounds involved a simple reaction site blocking. For both monoamine and diamine compounds, the inhibition performance was found to increase with increasing corrosion inhibitor concentration and decrease with acid concentration.

Aromatic and multiple bonds substituents introduced to monoamine and dimamine compounds were found to enhance inhibition performance compared to the starting materials (dodecylamine and 1, 12-dodacanediamine). This is attributed to the π-electrons present in aromatic and multiple bonds substituents. Both dodecylamine derivatives with a triple bond or an aromatic substituent exhibited excellent protection in 4.1 M HCl. However, the derivative with a triple bond showed the best protection (98%) at 7.7 M HCl. This result is very promising and suggests that this corrosion inhibitor has a good potential to be used as a corrosion inhibitor in oil/gas wells acid stimulation treatments.

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