(533j) The Characterization of Corrosion Inhibitors from Quinazolinones and Benzoxazines Derivatives By Electrochemical Methods

Corrosion of metals remains one of the most challenging aspects of industrial maintenance as it causes gradual damage to various vital parts and instruments of an industrial process. It is also one of the major setbacks of many marine systems as they are continually exposed to conditions ideal for corrosion. Many industries have incurred huge costs due to corrosion-related damages; therefore, the development of efficient corrosion inhibitors is of utmost urgency.

Organic compounds are among the most common corrosion inhibitors which protect the metal by adsorbing onto its surface. Earlier research has identified quinazoline compounds as corrosion inhibitors. In this study, the corrosion inhibitive properties of the following quinazolinone compounds: 3-amino-2-methylquinazolin-4(3H)-one (Q1), 3-amino-2-phenylquinazolin-4(3H)-one (Q2), and benzoxazine compounds: 2-methyl-4H-3,1-benzoxazin-4-one (B1), and 2-phenyl-4H-3,1-benzoxazin-4-one (B2) on mild steel were characterized. The structure-activity relationship (SAR) of selected derivatives shows higher adsorption to the metal surface. The corrosion inhibition depends on factors such as concentration of the organic ligand, stability of the ligand, the position of the heteroatom, and other physical factors. They were characterized by potentiometry, weight loss, and EIS experiments, which show great agreement with the hypothesis that these ligands can be used as an effective corrosion inhibitor. The selected quinazolinones and benzoxazines are much more stable across a broad range of pH, which could be attributed to the organic ligands easily adsorbing to the metal surface. Q2 and B2 have comparatively higher steric factors and therefore have a higher potential to prevent the oxidation of the metal surface. The functional groups of the selected ligands play a vital role in the H-bond formation of each ligand making a uniform monolayer. The carbonyl and amine groups of the organic ligands affect the unique adsorptive layer on the metal surface. Scanning tunneling microscopy images were also acquired to examine the surface morphology of the system which agrees with the prior experimental results. We conclude that the selected ligands can be utilized as effective corrosion inhibitors in various industries as they can withstand broad ranges of pH making them more durable.