Portugaliae
Electrochimica Acta

This work investigates the effectiveness of the ethanol extract of Phyllanthus amarus (EEPA) as a possible green corrosion inhibitor for aluminum in a HCl solution, using weight loss, linear and potentiodynamic polarization methods, in order to evaluate the inhibition efficiencies of the plant extract, at various concentrations. Scanning electron microscopy and Fourier transformed infra red spectroscopy were used to study the surface morphology and engagement of functional groups in the corrosion inhibition process. The results obtained at 303 K from weight loss, linear polarization resistance and potentiodynamic polarization methods recorded an inhibition efficiency that ranged from 56.65 to 69.17, 65.00 to 93.93 and from 51.38 to 79.96 %, respectively. Generally, the inhibition efficiency increased with higher concentrations, but decreased with a rise in temperature. The potentiodynamic study revealed that EEPA acted as a mixed type inhibitor, and formed an insoluble film, which protected the metal against corrosion. Examination of micrographs in the inhibitor presence and absence also confirmed the role of the protective film in blocking the corrosion active sites on the metal surface. Spectra analysis obtained from Fourier transformed infra-red study indicated that EEPA was adsorbed onto the aluminum surface via C=O and OH functional groups. The inhibitor adsorption was spontaneous, exothermic, and supported the physical adsorption mechanism. Calculated quantum chemical parameters for EEPA constituents revealed that Phyllanthusin D is the most active corrosion inhibitor in the compound. HOMO and LUMO diagrams of Phyllanthusin D supported the findings from FTIR analysis.

In the present work, we present the first study about the effect of Chamaerops humilis L. extract on the behavior of reinforcement steel in a carbonated concrete pore solution (pH≈9). This study has been realized using electrochemical measurements: open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS). The phytochemical screening was used to reveal the presence of some phyto-constituents in the plant extract. The Folin–Ciocalteu method and the AlCl3 coloration were used to determine the total phenolic and flavonoid contents, respectively. Results show that the plant extract has a beneficial effect on the development of a passive layer. The extract plays an important role in the corrosion potential evolution, and in the polarization resistance increase. The inhibition efficiency of the plant extract is close to 60% at a concentration of 0.75 g/L. Corrosion parameters also changed with exposure time.

The goal of our work is to develop, study, characterize and apply new epoxy macromolecular matrices in the coating process, and to optimize them in the conservation of marine heritage. Epoxy resins are technologically and nano-technologically compatible thermosetting macromolecule matrices, which are easy to use, thanks to their structures and viscosimetric and rheological properties, able to protect the heritage subject to atmospheric corrosion. In this paper, we tested the synthesized, crosslinked and formulated novel macromolecular nanoglycidyl trihydrazine 4,4,4-tripropoxy ethylene tribisphenol A (NGTHTPETBA), used as an anti-corrosive coating for E24 steel in 3.5% NaCl. In order to evaluate the inhibiting performance of the NGTHTPTBAE coating for E24 steel corrosion, and to examine its coating behavior, we applied the different E1(NGTHTPETBA/MDA) and E2(NGTHTPETBA/MDA/PN) formulations. The stationary and transient electrochemical studies are very revealing.

Benzyl dimethyl dodecyl ammonium chloride-zinc ion system, as quaternary ammonium salt (QA-Zn+2), was investigated as corrosion inhibitor for carbon steel in a 2.0 M sodium chloride solution, by different techniques such as weight loss, open circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopic techniques. The inhibition efficiency of the used system (QA-Zn+2) increases with increasing mixed inhibitor concentrations and with rising temperatures. A synergistic effect exists between QA and Zn+2. Potentiodynamic polarization curves indicate that the used system mainly acts as an anodic mixed inhibitor. The polarization resistance values were (Rp) increased, and the interface capacitance (Cdl) was decreased in the mixed inhibitor system (QA- Zn+2) presence, more than in the case of individual inhibitors. The corrosion inhibition is due to the adsorption of (QA-Zn+2) onto the metal surface, and the formation of a barrier film that separates the metal from the corrosive medium. The maximum inhibition efficiency of 98% was obtained at 200 QA and 50 ppm Zn+2 of the mixed inhibitor system, due to a synergistic effect.

The inhibitive action of Piper guineense (uziza leaf) extract on the corrosion of mild steel in a 2 M H2SO4 medium has been studied using weight loss method. The collected leaf samples were rigorously grounded and squeezed, with the resultant gel extract used for the weight loss determination at 1.0%, 2.0%, 3.0%, 4.0% and 5.0% v/v concentrations, respectively. Therefore, rectangular mild steel coupons in a 2 M H2SO4 solution were also employed to determine the amount of weight loss in the absence and presence of Piper guineense extract at temperatures of 303 K, 313 K and 323 K. The results show that mild steel corrosion inhibition increases with increasing concentrations of Piper guineense extract, showing greater efficiency at higher temperatures of 313 K and 323 K. Moreover, Piper guineense extract can effectively perform as a green and non-toxic inhibitor for mild steel corrosion in acidic environments.