Study of corrosion inhibition efficiency, mechanisms and application of chromones as corrosion inhibitors on alluminium, zinc and mild steel in acetic and sulphuric acids

MSc (Chemistry)

Department of Chemistry

This study focuses on investigating three chromone derivatives namely; 3-cyanochromone (3CYC), 6-methylchromone-2-carboxylic acid (6MC2C), and 6methylchromone hydrate (6MCH) as corrosion inhibitor for three metals namely, mild steel, zinc, and aluminium in 1.5 M of acetic acid, sulphuric acid, and nitric acid solution at 303K−333K. Techniques adopted in this study were electrochemical impedance spectroscopy (EIS), Potentiodynamic Polarization (PDP), Atomic Absorption Spectroscopy (AAS), and weight loss measurements to study the inhibition efficiency, corrosion mechanism, and the adsorption behaviour of chromone to metal surface. Fourier Transform Infrared spectrometry (FTIR) was useful to reveal the functional groups formed and disappeared during the interaction between the inhibitors and metal surface. 3D Optical Microscopic (3DOP) was utilised to investigate the surface morphology of metal in the presence and absence of corrosion inhibitors. These chromone compounds inhibited corrosion of zinc, mild steel, and aluminium in 1.5 M sulphuric acid, acetic acid, and nitric acid at 303K−333K. The effect of temperature on zinc, mild steel, and aluminium on inhibition efficiency obtained from PDP, EIS, AAS, and weight loss measurements shows that mild steel was affected severely with lower inhibition efficiency, however, these techniques shows that when the concentration of inhibitors increases, the inhibition efficiency also increases. A decrease in surface coverage occurs when temperature increases. EIS display an increase in the Rct value which lead towards an increase in the surface coverage of metal by the inhibitors. PDP reveals that the inhibitors successful affect cathodic and anodic half reactions almost equally. Weight loss measurements through ΔG° values reveal that the interactions of Al−inhibitor possess covalent nature and monolayer characteristics indicating chemisorption. It further shows physisorption character on Zn−inhibitor and MS−inhibitor. FTIR spectra displayed the disappeared and formed functional group bonds occurred when inhibitors interact with the metal surface. This implies that corrosion was minimised through this interaction forming Zn-inhibitor, MS-inhibitor, and Al-inhibitor complexes. 3DOP display rough metal surface when zinc, mild steel, and aluminium were exposed in sulphuric acid, acetic acid and nitric acid. The roughness when 3CYC, 6MCH, and 6MC2C were introduced was minimal, indicating the protection offered by these inhibitors to the metal surface. The information gathered shows that these three chromone derivatives successfully reduce the melting of zinc, mild steel, and aluminium in acidic medium

NRF