A new series of synthesized compounds as corrosion mitigator for storage tanks: Detailed electrochemical and theoretical investigations

Two new acridinedione namely 3,3,6,6-Tetramethyl-9,10-diphenyl-3,4,6,7,9,10-hexahydro-1,8-(2H,5H)-acridinedione (ACD-1), and 9-(4-methoxyphenyl)-3,3,6,6-tetramethyl-10-phenyl-3,4,6,7,9,10-hexahydroacridine-1,8(2H,5H)-dione (ACD-2) were synthesized and tested as prominent inhibitors for N80 steel corrosion inhibition in 15% hydrochloric acid (HCl). The weight loss result showed maximum efficiency of 97.3% (ACD-2) and Langmuir isotherm model best explained the adsorption of ACDs. EIS study reveals R_ct value increased to a maximum of 816.4 Ωcm² with the inhibition efficiency of 95.6% at 600 mg/L (ACD-2). The results of PDP proposed that ACDs are mixed but cathodic dominance inhibitors. The scanning electron microscopy (SEM) and atomic force microscopy (AFM) tests supports the adsorption of ACDs molecules onto the N80 steel surface. Intermolecular interactions and dynamics were studied using density functional theory (DFT) and molecular dynamics (MD).