Waste natural materials for sustainable corrosion prevention of steel: A mini review on their popularity, experimental and computational investigation, applications, challenges, and future strategy

Inhibitors have been proven successful and effective in controlling corrosion rates. However, their cost and harmful side effects are bothering them. Hence, natural materials (NMs) are in high demand for many years. NMs are considered a rich source of various active molecules that can build a protective layer to shield metals in corrosive environments. Based on the reported results, the NMs are found to be highly efficient (>95 % in some cases). The reason is adsorption of their phytochemicals on metals and blockage of corrosive molecules to the surface. Theoretical approaches like density functional theory (DFT) calculations and Monte Carlo (MC) as well as molecular dynamics (MD) simulations, are also used for accessing and comparing their performance. To achieve more economic and environment-friendly inhibition, waste natural materials (WNMs) have also been widely investigated. All the investigations advocated that they are very useful and could be a good replacement for synthetic inhibitors for various applications. However, there are some associated challenges, too. Their degradation at high temperatures, the inability of long-term protection, high concentrations in some cases, a reduced life cycle, the need for dedicated purification, efficient synthesis procedures, and more scientific selection are the few major challenges. This review provides a view of the NMs and WNMs that have been used for corrosion protection in various applications in the last twenty years and discusses their utilities, challenges, and future scopes, with additional details based on the analysis.