Which anthocyanin is the best corrosion inhibitor?

Abstract

Anthocyanins are one of the major dyes in plants. They have an aromatic and heteroatom within their framework structure so that anthocyanins are likely to be bound to metal surfaces via heteroatoms or π-π interactions. This property leads to the potential application of anthocyanins as corrosion inhibitors. However, there are challenges in determining the best anthocyanin for corrosion inhibitors due to the structure of anthocyanins are closely similar. The understanding of the corrosion inhibitor donor-acceptor properties is the simplest method to predict the corrosion inhibition performance of the targeted compounds. Therefore, the aim of this research is to predict the best anthocyanin for corrosion inhibition in the term of their electron transfer ability. The study presented the structures, the frontier molecular orbitals and the donor acceptor map of anthocyanins as corrosion inhibitor. A density functional theory at B3LYP level of calculation was performed systematically in an attempt to predict the corrosion inhibition properties based electron transfer ability of the ten well known anthocyanins: cyanidin (CN), aurantinidine (AU), delphinidine (DP), eropinidine (EU), luteonidine (LT), pelargonidine (PL), malvinidine (MV), peonidine (PE), petunidine (PT), rosinidin (RS). The theoretical prediction suggested that the corrosion inhibitor performances followed the order of DP > EU > CY >PT >MV > PE > RS > LT > AU > PL. The DP molecule has more number of hydroxyl (OH) groups than other anthocyanins, so that DP transfers more electrons to form stronger bonds with metals. The study will contribute to the design of new high inhibition efficiency of anthocyanin-based corrosion inhibitor.