Plant Extracts as Green Corrosion Inhibitors

Abstract

Adsorption inhibitors are considered efficient due to their structural characteristics, such as high electron density and heteroatom groups that can adsorb onto and protect metallic surfaces. Adsorption involves interaction between organic molecules and the metallic substrate, mainly in acidic or saline media. Factors such as temperature, immersion time, inhibitor concentration, and the presence of intensifiers or surfactants favor this process. As previously reported, higher temperatures can improve inhibition efficiency when molecules are chemically adsorbed, while performance declines in physically adsorbed molecules. Efficiency increases over short immersion times and stabilizes thereafter, whereas longer exposure can lead to molecule desorption and decreased efficiency. Substances like surfactants and ions can assist in the adsorption process. The predominant type of adsorption results from the structural characteristics of the inhibitor molecules that combine synergistically with other compounds. Plant extracts are a complex mixture of organic compounds, primarily alcohols, phenols, amines, amides, ethers, and others. Extraction conditions influence the type and amount of compound extracted. Water and ethanol have been used as solvents under temperatures up to 353 K. Increased temperatures improve compound solubility and diffusion rate, although excessively high temperatures should be avoided since they may cause the compounds to decompose.