Alkaloids as green and environmental benign corrosion inhibitors: An overview

Alkaloids are naturally occurring nitrogen containing organic bases that possess diverse and significant physiological effects on animals and humans. They are mostly derived from the plants. Because of their natural and biological origin, they (alkaloids) are considered as environmental benign alternatives to be used as corrosion inhibitors at the place of traditional and toxic synthetic corrosion inhibitors. Numerous alkaloids have been employed as effective corrosion inhibitors for metals and alloys in different electrolytic media. It has been established that alkaloid molecules are associated with extensive conjugation in the form of non-bonding and π-elections through which they can interact strongly and inhibit corrosion efficiently. Present review article features the collection of reports published on the topic alkaloids as corrosion inhibitors. In this review article, we also described the corrosion and its adverse effect, mechanism of corrosion and corrosion inhibition by organic corrosion inhibitors (including alkaloids) and factors affecting the inhibition property of corrosion inhibitors. Literature study suggests that most of the alkaloids are soluble in the polar electrolytic media and thereby behave as good corrosion inhibitors. Present review article describes the inhibition effect of several classes of alkaloids such as pyridine, purine and indole derivatives that have been used previously. Chemical structures alkaloids and their mode of adsorption and interactions with the metallic surface, nature of metal and electrolyte and related salient features have also been tabulated in the review.