Plants Polyphenols: An Alternative Source for Green Corrosion Inhibitor

Mohd Jain Kassim, Tan Kang Wei

Abstract


Corrosion inhibitors are chemical compounds when added in a small
concentration to the corrosive environment will significantly reduced the corrosion rate of metals or its alloys. The environmental toxicity of organic and synthetic corrosion inhibitors has prompted the search for green corrosion inhibitors as they are biodegradable, do not contain heavy metals or other toxic compounds. As in addition to being environmental friendly and ecologically acceptable, plant products are inexpensive, readily available and renewable. Although substantial research has been devoted to corrosion inhibition by plant
extracts, reports on the detailed mechanisms of the inhibition process and identification of the active ingredient are still scarce. Most plant extracts constitute of oxygen and nitrogen containing compounds. Most of the oxygen-containing constituents of the extracts is a hydroxy aromatic compound such as polyphenolic compound. It is postulated that a number of OH groups around the molecule lure them to form strong links with hydrogen and form complexes with metals. The complexes caused blockages of micro anodes and/or micro
cathodes and hence retard the subsequent dissolution of the metal. Another suggestion was through and adsorption of polyphenols to the metals due to the presence of donoracceptor interactions between the π-electrons of aromatic ring and vacant d orbital of surface metal atoms. The present paper will highlight some of Malaysian plant extracts which are potential to be used as corrosion inhibitors for mild steel in acidic media


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