Portugaliae
Electrochimica Acta

This work examined MLE as Zn corrosion inhibitor in a NaOH medium. MLE was subjected to qualitative and quantitative Pc analyses. Thermometric and gravimetric techniques were employed in the corrosion inhibition study. In the thermometric method, reaction numbers for Zn dissolution in blank and inhibited NaOH media were used to determine MLE IE(%). The gravimetric method was carried out using one factor at a time and RSM. CCD of DES was employed in RSM. The analyses of the experimental results revealed that MLE was predominantly made up of flavonoids, alkaloids and tannins (471.7, 458.3 and 115.0 mg/100 g, respectively). Zn  by the extract increased with higher inhibitor C, but decreased with a rise in T. A quadratic model adequately described the relationship between IE(%), C, T and time factors. High IE(%) of 83.75% was obtained at an inhibitor C of 1.0 g/L, T of 303 K and IT of 5 h. Hence, MLE is a suitable inhibitor for Zn corrosion in a NaOH medium. Keywords: corrosion inhibitor, MLE, NaOH and Zn.

The present study has investigated electrolysis conditions, in which spatiotemporal structures onto the cathode surface could be observed for the first time, under strictly controlled settings, during Cu-Sb alloy ED. Self-organization phenomena, such as in depth self-assembled deposits structures, appeared when Sb content was higher than 70 wt% in the coatings. The layers and their structures different optical and morphologic areas were characterized. Keywords: Cu-Sb alloy; ED; multilayers; self-organization.

Inhibition of MS corrosion in a 3% NaCl solution, by glasses containing Ti-0, Ti-5 and Ti-7, in different C, was investigated using AFM, EIS, FTIR spectroscopy, PPD, SEM and XRD techniques. PPD and IES gave IE(%) of 92.8, 99 and 98.3%, and 91.9, 98 and 98.3%, for Ti-0, Ti-5 and Ti-7 glasses, respectively, at optimum C (0.4 g/L). In addition, EIS results indicated that IE(%)increased with higher C of Ti in the glasses, reaching its maximum at 7% TiO2. The three studied compounds acted as anodic inhibitors, though anodic reactions were more suppressed than the cathodic ones. SEM revealed that the inhibitors significantly stopped the attack by Cl- ions, through chemical adsorption onto the MS surface. Keywords: Ti-0, Ti-5 and Ti-7 glasses; MS; 3% NaCl; AFM; EIS; FTIR; PPD; SEM; XRD.

U2 and U4 were successfully synthesized from C7H6N2 N-alkylation (general and useful route to quaternary ammonium salts NH4Cl from tertiary amines) with alkyl bromides. The products were further alkylated to the corresponding ILs: U5 and U7. All the synthesized compounds were characterized by spectroscopic techniques, and their compositions were established through elemental analysis. The synthesized compounds were investigated as inhibitors for MS corrosion, using 1 M HCl as a model solution. WL experiments, surface analysis, quantum chemical calculations and MD simulation methods were used for evaluating the inhibitors anticorrosion properties. The results showed that ILs possessed remarkable inhibition properties under the studied conditions. U5 displayed the highest IE of 95.22%, at 200 ppm. ILs corrosion IE(%) was ascribed to their adsorption onto the MS surfaces, which followed the Langmuir’s isotherm. SEM revealed the formation of a barrier film by the inhibitors on the MS surface. Finally, the experimental results were corroborated by theoretical quantum chemical calculations and MD simulation studies. The studied inhibitor molecules interaction energies with the Fe surface followed the order U5 > U7 > U2 > U4, which is consistent with the experimental data. Keywords: corrosion inhibition, ILs, MD simulations, MS, N-alkylbenzimidazoles, quantum chemical calculations and SEM.

MS acceptability for nowadays structural construction is premised on its availability and low cost. However, due to MS poor corrosion resistance, most especially in acidic and alkaline environments, there have been increasing concerns about its use. The use of inhibitors, as proposed by different researchers, mitigates MS CR, thus reducing the economic losses experienced by all chief users of this alloy. In recent years, scientists have focused on green inhibitors obtained from plant, fruit and vegetable extracts, and essential oils. Besides being environmentally friendly, in terms of corrosion resistance, plant extracts are becoming increasingly important, due to their low cost and toxicity, and high availability. Additionally, they are rich in organic compounds with polar atoms, such as O, P, S and N, containing multiple bonds in their molecules, through which they can adsorb onto the metal surface, forming a protective film, by various adsorption isotherms. This paper provides a review on research works done so far on MS corrosion control by naturally occurring plant extracts as corrosion inhibitors, in both acidic and alkaline environments, where this alloy is mainly applied. Keywords: plant extracts; CR; inhibition; MS; adsorption isotherms; environments.