8–Hydroxyquinoline is key to the development of corrosion inhibitors: An advanced review

• 8HQ is excellent green source for next generations of corrosion inhibitors. • Corrosion inhibition efficiency of 8HQ and its derivatives are over 95–98 % at 10 −3 M. • 8HQ is easily modified with the organic heterocyclic compounds and natural polymers. • some halogen atoms (Br, Cl) provide the synergism effect with the 8HQ. • 8–HQ molecules are easily and rigid chemically and physically interacting with the metal surface. 8–Hydroxyquinoline (8–HQ) is known for its strong coordination and chelation behaviours. Because of this, 8–HQ and its derivatives manifest exceptionally high potential for corrosion inhibition. Using the nonbonding electrons of oxygen and nitrogen, 8–HQ and its derivatives coordinate strongly with metallic surfaces, which results in strong inhibition of corrosion. The current assessment considers a collection of reports on the corrosion inhibition potentials of 8–HQ and its derivatives. 8–HQ and its derivatives become effectual by adsorbing on the metal surface, and the adsorption mode is physiochemisorption. Corrosion inhibition by HQ derivatives is highly dependent on the natures of the functional groups. Literature studies have specified that 8–HQ and its derivatives serve as mixed–type inhibitors that retard both anodic and cathodic Tafel reactions. Moreover, after adsorption, 8–HQ and its derivatives build layers between metal surfaces and electrolytes that behave as barriers to charge transfer processes. Adsorption mainly follows the Langmuir adsorption isotherm. The results of literature studies indicate that 8–HQ derivatives bind with metal surfaces via charge transfer processes, achieve flat alignment and deliver high superficial coverage. This review will be important in developing a new generation of corrosion inhibitors based on 8–HQ and its derivatives.