Portugaliae
Electrochimica Acta

The corrosion inhibition effect of 1-octyl-2-(octylthio)-1H-benzimidazole (T3) on mild steel in a 1 M hydrochloric acid solution was studied using weight loss measurement, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques, at 308 K. This compound has exhibited a corrosion inhibition efficiency of 93% at 10-3 M concentration. The adsorption of this molecule onto the mild steel surface obeyed Langmuir adsorption isotherm. Potentiodynamic polarization measurements indicated that the studied compound acted as a mixed type corrosion inhibitor. EIS results showed that an increased inhibitor concentration led to an increase in the polarization resistance and decrease in the double layer capacitance.

The present study aimed to evaluate the inhibition effect of an organic compound, namely, (E)-N'-(2-hydroxybenzylidene)isonicotinohydrazide (BIH), for carbon steel corrosion in a 1.0 M HCl solution, by using weight loss (WL), potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS). Results show that BIH is a good inhibitor, and the percentage of inhibition efficiency increases on its higher concentrations. The maximum inhibition efficiency of 94% was obtained at 5×10-3 M. Polarization studies revealed that the BIH compound acts as a mixed type inhibitor. EIS showed that increasing the concentration of the inhibitor led to an increase in the charge transfer resistance and a decrease in the double layer capacitance. It was found that the adsorption of this compound obeyed the Langmuir adsorption isotherm. The associated activation energies and thermodynamic parameters of the adsorption process were evaluated and discussed. The temperature effect was studied in the range from 303 to 333 K. In addition, quantum chemical calculations based on the density function theory (DFT) and Monte Carlo simulations were done to support the experimental results.

This paper reports the fabrication of a lithium ion supercapacitor from vertically-aligned carbon nanotubes (VACNTs) directly grown on a conductive substrate (SUS 310S alloy), using alcohol catalytic chemical vapour deposition technique. CNTs direct growth technique on an electrically conducting foil simplifies the electrode assembly, thus reducing the fabrication process, because the foil can directly act as a current collector. With the VACNT direct growth technique, the supercapacitor electrode was easily prepared and assembled with a non-aqueous 1 M LiPF6 electrolyte. Experimental results show that CNTs (multi-walled type structures of good quality) were perpendicularly grown to the substrate. This device demonstrates a specific capacitance of up to 101 F g-1 (at a scan rate of 1 mVs-1), and a high-rate capability, up to a scan rate of 1000 mVs-1. The VACNT electrode electrochemical performance was also measured by galvanostatic charge-discharge and electrochemical impedance spectroscopy. The effect of free standing CNTs direct growth on the current collector makes insulating binder material unnecessary, thus producing better ion accessibilities to its surface. This also contributes to the good and reliable electrochemical supercapacitor performance.

We developed and applied in our work a new polyepoxide polymer, decaglycidyl phosphorus penta methylene dianiline, to study its coating behavior in a marine environment. Then, we tested the new crosslinked and formulated macromolecular binder (DGPMDAP), which is used as an anticorrosive coating on E24 carbon steel, in 3.5% NaCl. So as to evaluate and examine the DGPMDAP coating performance in the field of E24 carbon steel corrosion, we applied the different E1 (DGPMDAP/MDA) and E2 (DGPMDAP/MDA/PN) formulations on the metal substrate. The stationary and transient electrochemical studies are very interesting; and, in order to confirm the obtained results, we dispersed the charge of the natural phosphate that was incorporated in the E2 (DGPMDAP/MDA/PN) macromolecular matrix, through the use of a polarizing optical microscope.

Quaternary Ni-B-W-Mo coatings were deposited on AISI 1040 steel by the electroless method. Some of the specimens were heat-treated at 300, 350, 400, 450 and 500 °C, for 1 hour. The deposited coatings contained a high weight percentage of W, and a low B content was detected by energy dispersive X-ray analysis. The coatings in as-deposited state were amorphous, and heat treatment resulted in crystallization with the precipitation of borides. W and Mo were present in the coatings, mainly in a solid solution form. The surface morphology study revealed densely nodulated structures, which are pertinent for sodium borohydride reduced electroless nickel coatings. Electrochemical impedance spectroscopy studies were conducted to determine the corrosion resistance of the as-deposited and heat-treated coatings in a 3.5% NaCl electrolyte. The corroded surfaces were observed under scanning electron microscope, to study the corrosion mechanism.