The performance of the Galactomannan as a green inhibitor to protect the carbon steel against corrosion

Carbon steel suffers from high degradation in an acidic medium like acidic stripping. For this reason, the protection of the carbon steel from the aggressive acidic attacks is required. One of the most common methods of protection is the use of corrosion inhibitors. For environmental reasons, researchers have investigated a new generation of inhibitors, called green inhibitors that cause less damage to the environment while providing high protection efficiency against corrosion.

This study aims to evaluate the impact of a bio-sourced polymer as a corrosion inhibitor against iron corrosion in a 1 M HCl solution. Galactomannan was obtained from the Ceratonia Siliqua L. seeds, and its structure was characterised by using Fourier tranformation infrared spectroscopy (FTIR). Effects of the inhibitor concentration and immersion time on the corrosion resistance of iron was evaluated using different electrochemical methods (Tafel curves, impedance diagrams). Ability of the Galactomannan molecules to form links with iron atoms was characterised using UV-visible analysis. Surfaces of the corroded specimens was evaluated by using scanning electron microscopy (SEM) and EDS.

The results show that the Galactomannan acts as a mixed type inhibitor by physisorption and chemisorption on the metal surface. Besides, the efficiency of this compound increases with the concentration of the inhibitor and reaches a value of 87.72% at a concentration of 1 g/l.