Supramolecular corrosion protection: Eco-friendly synthesis and efficacy of a β-cyclodextrin/o-phenylenediamine complex

In corrosion science, organic inhibitors were widely used to protect the metal from corrosion. However, the greenness and effectiveness are a problem for organic inhibitors. Therefore, environmentally friendly and cost-effective corrosion inhibitors are important tasks in the material and engineering sciences. The solubility of organic inhibitors are also problem. In this work, these solutions were tried to solve. In this research work, the green supramolecular complex (β-CD/o-PhDA) was first synthesized from the β-cyclodextrin (β-CD) and o-phenylenediamine (o-PhDA). The structure, physical interactions and structural changes of β-CD/o-PhDA were confirmed by the FT-IR, 1H NMR and Raman spectroscopic results. It was found that the supramolecular system of β-CD/o-PhDA was more stable with the van der Walls and hydrophobic interactions. The corrosion inhibition performance of β-CD/o-PhDA on the St20 steel corrosion in 0.5 M hydrochloric acid (pH=0.3) was first investigated by various experimental and theoretical investigations. It is indicated that the corrosion protection of β-CD/o-PhDA was over 95–96% in the aggressive solutions. The β-CD/o-PhDA formed the thin defender layer on the metal surface by the formation of NFe and FeO bonds. The protonation process affects the corrosion inhibition of the host-guest complex on the metal surface. The adsorption energies of β-CD/o-PhDA on the metal surface are more negative and depend on the adsorption positions. The β-CD/o-PhDA acts as a mixed type of corrosion inhibitor. The β-CD/o-PhDA was suggested as good water soluble, low-cost, stable and green protective agent for the acidizing-scaling processes in the chemical industries.