Study on the scale and corrosion inhibition of amino acid and sulfonic acid modified polyaspartic acid.

To improve the scale and corrosion inhibition ability of polyaspartic acid (PASP), the modified PASP scale and corrosion inhibitor Trp-ASA-PASP was prepared by graft modification of PASP with tryptophan (Trp) and aminomethanesulfonic acid (ASA). The synthetic products were characterized by infrared spectrosco-py, and the critical supersaturation method of calcium carbonate combined with field emission scanning electron microscopy (SEM) was used to analyze the scale and corrosion inhibition performance of PASP and Trp-ASA-PASP. The results showed that the relative supersaturation value (Sr) of Trp-ASA-PASP was always higher than that of PASP as the scale inhibitor dosage increased, indicating that the scale inhibition ability of Trp-ASA-PASP was better than that of PASP. The corrosion inhibition performance of Trp-ASA-PASP on A3 carbon steel was evaluated by electrochemical method combined with weight loss method. Quantum chemical calculations based on density flooding theory were used to compare the scale inhibition performance of Trp-ASA-PASP with that of PASP. The reactive sites and orbital energy gap (AE) of PASP and Trp-ASA-PASP, and their adsorption and binding ability to metals were compared based on density flooding theory to further reveal the corrosion inhibition mechanism of Trp-ASA-PASP. The results showed that Trp-ASA-PASP is a mixed cathodic-anodic corrosion inhibitor with an anodic bias, and the corrosion inhibition rate increased with the increase of its concentration. The orbital energy gap AE (Trp-ASA-PASP) was 4.3482 eV smaller than that of AE (PASP) which was 6.9634 eV, indicating that Trp-ASA-PASP is more likely to interact with metals, and the reaction active site of Trp-ASA-PASP was mainly in the orbital energy gap. The reactive site of Trp-ASA-PASP is mainly located on the sulfonic acid group of the side chain, which is more likely to accept electrons from the metal surface than PASP and interact with the metal to form a protective film on the metal surface to achieve the corrosion inhibition effect. [ABSTRACT FROM AUTHOR]