Regioselective synthesis of multi‐functionalized benzopyranophenazine derivatives: Comparative studies on corrosion inhibition efficiency on mild steel in 1M H₂SO₄ solution

Abstract

ObjectivesA regioselective approach has been developed for the synthesis of benzopyranophenazine derivatives using In (OTf)3 as a catalyst in one‐pot synthesis. Further, these synthesized compounds were successfully used as organic corrosion inhibitors on mild steel in 1M H2SO4 solution.MethodsThe synthesized organic inhibitors were confirmed using NMR, and HRMS and their regioselectivity was confirmed by DFT studies using the B3LYP/6‐31G (d, p) basis set. Further, the corrosion, and inhibition efficiencies were confirmed by various methods such as weight loss technique, electrochemical impedance spectroscopy, and potentiodynamic polarization studies.ResultsThe two synthesized compounds MBPPand BBPP show excellent corrosion inhibition properties than the previously reported organic inhibitors, especially, the electron‐donating nature of methoxy‐substituted phenazine derivatives show superior corrosion inhibition properties as 98.96 in 900 ppm than electron withdrawing bromo substituted phenazine derivative in the same concentration which indicates that the electronic structure of the organic inhibitor plays an important role in the corrosion inhibition efficiency of mild steel in an acid medium.ConclusionThe synthesized compound efficiently inhibits the corrosion on the mild steel surface and it forms a barrier on the metal surface. As a result, the phenazine derivatives of both MBPP and BBPP act as very effective corrosion inhibitors and the electron‐donating nature of MBPP shows more inhibition efficiency than BBPP inhibitors.