Mechanism of Inhibitive Action of Dl-Methionine Towards the Corrosion of Mild Steel in Hydrochloric Acid Solution

DL-methionine has been investigated as inhibitor for the corrosion of mild steel in 1.0M hydrochloric acid solution using weight loss method and Scanning Electron Microscope (SEM) analysis. The investigated results showed that the inhibition efficiency increases with the increase in concentration of the inhibitor and decreases with the increase in temperature. SEM analysis indicated that the metal surface was in a better condition in the presence of inhibitor than the specimen exposed in the absence of the inhibitor. DL-methionine acted as a very good inhibitor and is also environmentally friendly, non -toxic, biodegradable and relatively cheap. Keywords: DL-methionine, mild steel, SEM, Corrosion inhibitor.

Anti-Corrosion Behavior of Olmesartan for Soft-Cast Steel in 1 mol dm−3 HCl

This study discusses the effects of temperature on corrosion inhibition for soft-cast steel by the pharmaceutically active drug olmesartan in 1 mol dm−3 HCl. The sufficient number of electron-rich elements and non-bonding π electrons in its structure favored a good capability for coating onto the electron-deficient steel surfaces. Theoretical and electrochemical measurements were carried out at the temperature region of 303 K to 333 K. Therefore, the experiment suggests that the inhibition efficiency of olmesartan increases with its increasing concentrations due to the adsorption. Additionally, even at a higher temperature of 333 K, the inhibitor molecules attain their stability towards corrosion resistance of steel surfaces. The adsorption of inhibitors on steel surfaces is spontaneously found to include the mixture of physisorption and chemisorption, and it obeys Temkin’s adsorption isotherm model. Theoretical and computational considerations were made using quantum chemical parameters and molecular dynamics simulations, which confirmed that the olmesartan has a suitable corrosion inhibitive capability intended for soft-cast steel in 1 mol dm−3 HCl. Additionally, scanning electron microscopic measurement was used to obtain a visual idea of the inhibitive action of the inhibitor attained by forming an adsorbed protective layer onto the steel surfaces. The minute concentration of olmesartan of about 10–50 ppm shows high inhibition efficiency of ~80%, even at elevated temperatures.

Study of the corrosion-inhibiting activity of the green materials of the Posidonia oceanica leaves’ ethanolic extract based on PVP in corrosive media (1 M of HCl)

Since the corrosion protection of mild steel samples in corrosive media (1 M of hydrochloric acid [HCl]) was cheap and successful, the ethanol extract of Posidonia oceanica leaves based on polyvinylpyrrolidone (P. oceanica/PVP) was analyzed using the weight reduction, the open circuit potential, and the potentiodynamic polarization methods. The obtained results explained that the productivity of hindrance increments had the greatest restraint efficiency of ∼81% at 1,000 ppm, as the concentration of the extract increased. Liable for adsorption as a thin layer on the surface of mild steel to protect it, the creation of kaolin-traced phenolic and polysaccharide compounds was confirmed by the Fourier transform infrared spectroscopy analysis. A scanning electron microscope was used to evaluate the inhibitive action of P. oceanica/PVP against steel in corrosive media and the change in surface morphology was considered. It is presumed that the ethanol removed from the Posidonia oceanica leaves can fill in as a compelling consumption inhibitor for gentle steel in HCL solution (1 M).

The inhibitive action of Plukenetia conophora plant extract on the corrosion of Al–Zn–Cu alloy in different acidic media

Plukenetia conophora (Nigerian Walnut) leaf extract was studied as a corrosion inhibitor on Al–Zn–Cu alloy in acidic (HCl and H2SO4) media using gravimetric, gasometric and electropotential techniques. The study showed that the inhibition efficiency (IE) increased as the concentration of the leaf extract increased and reached the peak (94.8%) at 0.8 g/L in 1 M HCl. In the two acidic media, P. conophora leaf extract exhibited good corrosion inhibition properties on the Al–Zn–Cu alloy samples due to adhesion of the extracts on the samples' surfaces. The adsorption process of the extract on the alloy sample surfaces was found to be spontaneous and perfectly obeyed the Langmuir isotherm model. Thus, P. conophora leaf extract is recommended for utilisation as a potential replacement for toxic inorganic inhibitors and for application in paint and coating industries.