Corrosion Inhibition Studies of Metals in Acid Media by Fibrous Plant Biomass Extracts and Density Functional Theory: A Mini-Review

Metals used in industries are exposed to several processes such as acid cleaning, pickling, and descaling, which leads to corrosion. A good measure of corrosion control has been achieved by reducing the metal impurity content, by corrosion inhibition, the use of modification techniques, and the incorporation of alloying elements. However, the use of corrosion inhibitors seems to be the most economical and practical of the methods. Besides, the use of fibrous plant biomass as corrosion inhibitors has become important as a suitable substitute for the toxic chromates, phosphates, and arsenic-based inhibitors. The constituents in the fibrous plant biomass extracts react with the metal ions on a corroding metal surface forming organometallic complexes. The recent introduction of Density Functional Theory (DFT) in the theoretical study of the electronic structures elucidates the adsorption modes and the individual contributions of the plant extracts. The DFT has proven to be a significant contribution to the conventional methods based on gravimetry, gasometry, and electrochemical investigations for studying corrosion inhibition. This review provides insights into the use of fibrous plant extracts as corrosion inhibitors in acid solution as well as the DFT calculations.