An extensive analysis of isoindigotin derivatives as effective corrosion inhibitors for mild steel in acidic corrosive environments: An electrochemical and theoretical investigation

• Published in: Progress in organic coatings Vol. 200; p. 108960
• Main Authors: Li, Mingzhe, Fu, Shaopeng, Peng, Yichun, Sang, Tingting, Cui, Chenyu, Ma, Hongmei, Dai, JinPeng, Liang, Zezhou, Li, Jianfeng
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.2025
• Subjects: Adsorption film; Green corrosion inhibitor; Isoindigo derivatives; Mild steel; Theoretical calculation; Mild steel; Theoretical calculation; Green corrosion inhibitor; Adsorption film; Isoindigo derivatives
• ISSN: 0300-9440
• DOI: 10.1016/j.porgcoat.2024.108960

Isoindigo and its derivatives are frequently employed as active ingredients in pharmaceuticals and in solar cells, largely due to their distinctive structural characteristics, which render them a green substance. The utilization of its polymers as efficacious corrosion inhibitors for the safeguarding of mild steel exhibits considerable promise. In order to achieve this, a green and highly efficient isoindigo polymer (E)-7-(9,9-bis(3-(dimethylamino) propyl)-9H-fluoren-2-yl)-1,1′-bis(3-(dimethylamino) propyl)-[3,3′-biindolinylidene]-2,2′-dione (PIIDN-FN) was synthesized using a simple one-step polymerization reaction and subsequently employed as a corrosion inhibitor for the first time. In this work, its ability to inhibit the corrosion of Q235 when added to 1 M HCl medium was the subject of corresponding electrochemical tests and surface analyses (including SEM, AFM and XPS etc.). The results implied that PIIDN-FN was able to achieve a maximum inhibition efficiency of 94.52 % at a concentration of 100 mg L−1, and the inhibition efficiency was still close to 90 % even at a high temperature of 328.15 K. Moreover, the PDP results indicated that PIIDN-FN is a hybrid corrosion inhibitor, and it was determined that the adsorption of the material onto the carbon steel surface conformed to the Langmuir isotherm model. Furthermore, quantum chemical calculations (QC) based on density functional theory (DFT) and molecular dynamics simulations (MD) facilitated the elucidation of the inhibition mechanism. The findings of the theoretical investigation suggest that PIIDN-FN adsorbs as a film on the surface of mild steel due to its conjugated structure, forming a complex with iron and thereby providing effective protection for carbon steel. •Synthesis of PIIDN-FN polymer by one-step polymerization reaction.•PIIDN-FN corrosion inhibitor efficiently prevents MS corrosion in acidic environments.•At ambient temperatures up to 328 K, corrosion inhibitor efficiencies close to 90 %.•Theoretical calculations were used to elucidate the corrosion inhibition mechanism of PIIDN-FN.