Green Inhibitors for Corrosion Protection of Metals and Alloys: An Overview

Abstract

Corrosion control of metals is of technical, economical, environmental, and aesthetical importance. The use of inhibitors is one of the best options of protecting metals and alloys against corrosion. The environmental toxicity of organic 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 environmentally friendly and ecologically acceptable, plant products are inexpensive, readily available and renewable. Investigations of corrosion inhibiting abilities of tannins, alkaloids, organic,amino acids, and organic dyes of plant origin are of interest. In recent years, sol-gel coatings doped with inhibitors show real promise. Although substantial research has been devoted to corrosion inhibition by plant extracts, reports on the detailed mechanisms of the adsorption process and identification of the active ingredient are still scarce. Development of computational modeling backed by wet experimental results would help to fill this void and help understand the mechanism of inhibitor action, their adsorption patterns, the inhibitor-metal surface interface and aid the development of designer inhibitors with an understanding of the time required for the release of self-healing inhibitors. The present paper consciously restricts itself mainly to plant materials as green corrosion inhibitors.

A Study of the Corrosion Inhibition of Mild Steel in 0.5M Tetraoxosulphate (VI) acid by Alstonia boonei Leaves Extract as an Inhibitor at Different Temperatures

“…The inhibition efficiency (I %) of Alstonia boonei leaves extract was computed using equation (2) [7] :…”

“…Corrosion inhibitors are commonly added in small concentrations to acids, cooling water, steam and other environments; either continuously or intermittently to reduce corrosion. Corrosion inhibitors reduce the rate of corrosion by adsorption of ion molecules onto the metal surface, increasing or decreasing the anodic and/or cathodic reaction, decreasing the diffusion rate for reactants to the surface of the metal and decreasing the electrical resistance of the metal surface [2]. Chemical based corrosion inhibitors have been successfully used to control the corrosion of metals and alloys in various media [3][4][5].…”

The inhibitory action of Bauhinia purpurea extracts on the corrosion of carbon steel in sulfuric acid medium

“…In this context, the search for corrosion inhibitors in acidic media to protect metallic surfaces has established the natural products as a rich and promising source. The protective efficiency appears to increase with the presence of oxygen, nitrogen, sulphur and π electrons in the organic compounds [1][2][3][4] . Apparently, the inhibition efficiency is linked to the polar functions that act as the reaction center for the adsorption process 5 .…”

“…The environmental toxicity of organic corrosion inhibitors has prompted the search for green corrosion inhibitors as they are biodegradable and do not contain heavy metals or other toxic compounds. Plant products are inexpensive, readily available and renewable 4 , as well as environmentally friendly and ecologically acceptable.…”

Solvents Effect on Thermal Stability and Electrochemical Behaviour of Griffonia Simplicifolia Extracts as Steel Corrosion Inhibitor in Acidic Environment

“…A vast number of plant extracts have been investigated and some of them have shown excellent inhibitive effects especially at low temperatures. [2][3][4] If plants that are meant for food are used to produce corrosion inhibitors, food scarcity may set in. Therefore, inedible plants and agricultural wastes are better options.…”