Journal of Materials Science Research and Reviews

The development of expired drugs into directly applicable corrosion inhibitors for metals in acidic media, will help not only help to solve the global problem of corrosion but will also offer legal and profitable outlets for extending the cradle to grave life of those materials and eliminate the need for their illegal resale as currently happens in many developing countries such as Nigeria. The expired, biodegradable and environmental drug; Isoniazid was evaluated for corrosion inhibition capability for API5L steel in 0.5M H₂SO₄ environment. Electrochemical Impedance Spectroscopy (EIS) reveals a drastic drop in corrosion rate when the pulverized form of expired isoniazid drug was introduced into 0.5M sulphuric acid environment containing immersed steel samples. The impedance diagram shows the same trend (one capacitive loop); however, the diameter of this capacitive loop increases with increasing concentration. The presence of the inhibitor increases the impedance but does not change other aspects of the behaviours. EIS showed that expired isoniazid drugs inhibits corrosion in mild steel in 0.5M H₂SO₄ in a mixed manner. Conversely, the rate of weight loss in the environment decreased with increasing concentration of expired isoniazid in the environment. Surface Analysis shows a progressive covering and thickening of adsorbed surface layer of expired isoniazid drug film on the immersed API5L steel surface with increasing concentration of the expired drug in the acid environment. The corrosion inhibition was considered to be via a mixed mode adsorption of a layer of expired isoniazid drug molecules across active corrosion sites, gradually cutting off metal-environment contact and thus shutting the relevant corrosion process. The level and effectiveness of achievable corrosion inhibition tend to increase with increased concentration of the expired isoniazid drug in the metal-acid environment.  All other evaluation methods support these conclusions.