CORROSION AND PROTECTION

INHIBITORS

Green Inhibitors Environment Metals
Papya seed extract HCl, H2SO4 Steel
Garlic extract HCl, H2SO4 Steel
Coffee ,caffeine HCl, H2SO4 Steel
Aloe vera HCl, H2SO4 Steel, Zn
Banana plant juice NaOH Concrete steel
Hibiscus sabdariffa leaves NaOH Al
Mango extract/ Orange Juice HCl Steel
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Green Inhibitor
 
Though synthetic compounds showed good anticorrosive activities, most of them are highly toxic to both human beings and environment. The safety and environmental issues of corrosion inhibitors  have  been a global concerned. They may cause  damage to organ system viz., kidneys or liver, or to disturb a biochemical process of  an enzyme system.
 Some natural occurring products extracts have been found to be  anticorrosion agents. They  are eco-friendly, harmless , biocompatible and  sustainable.

An inhibitor is a substance (chemical) when added in small concentration in ppm level to a corrosive environment like sea water, acid or other aqueous media, decreases the corrosion rate of a metallic structure in contact with the environment and its life is lengthened from few months to several years. The inhibitor gets adsorbed on the metal surface on anodic sites or cathodic sites or both , accordingly, it is called as anodic, cathodic or mixed inhibitor.

The inhibitor may be an inorganic compound like chromate , nitrate phosphate which passivates the metal or  an organic compound like thiourea, amones, octynol etc.. Organic compounds with multiple bonds or pi electron system  or aromatic compound make  good inhibitors by getting adsorbed on the metal surface by forming co ordinate bond with the metal surface through electron transfer