Portugaliae
Electrochimica Acta

Low-carbon steel electrodes were buried in sterilized and bacterial media. The potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) were sequentially carried out on buried electrodes. The corrosion potential, on the steel electrode buried in a sterilized medium (without sulphate reducing bacteria), was found to be more negative than that of the electrode buried in the sulphate reducing bacteria (SRB) medium. Cathodic and anodic curves electrodes buried in a SRB medium showed the highest current density. Clearly, three phases were observed during the SRB growth within an incubated medium. EIS measurements showed that the effects of biofilms on steel electrodes varied with time. From the bacterial medium, EIS results showed an optimum cathodic protection (CP) potential of -1450 mV Cu/CuSO4. Surface morphologies of electrodes buried in bacterial media revealed dimples on the entire electrode surface, when the slow strain rate tensile test (SSRT) was carried out in air, while quasi-cleavage was discovered on the steel electrode, when the applied CP potential was -950 mV Cu/CuSO4. At -1450 mV Cu/CuSO4, corrosion products were seen all over the electrodes, and a complete cleavage occurred on them at -1890 mV Cu/CuSO4.

The use of plant extracts as corrosion inhibitors has been increasing greatly in recent studies. The inhibitive effect of sumac, Rhus Coriaria (RC), a Lebanese plant, and Quercetin, one of its chemical constituents, on mild steel corrosion, in 0.5 M HCl and 0.5 M H2SO4 solutions, was studied using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, atomic force spectroscopy (AFM) and Fourier infrared spectroscopy (FTIR) techniques. Potentiodynamic polarization curves indicated that both RC and its chemical constituent, Quercetin, behave as a mixed type inhibitor in both acidic media. The dissolution process of RC and Quercetin occured under activation control, as showed by EIS measurements, and the corrosion inhibition is the result of the inhibitor adsorption onto the metal surface. Inhibition by RC extract was found to be greater in 0.5 M HCl than in 0.5 M H2SO4 solutions; RC extract also proved to be a better inhibitor than its chemical constituent, Quercetin, in both acids. Thermodynamic parameters indicate that the inhibition process on the steel surface was due to spontaneous physical adsorption of RC and Quercetin onto it. The adsorption model was found to obey thermodynamic-kinetic model and Flory-Huggins model. Surface analysis by AFM spectroscopy investigated the formation of the adsorbed protective film onto the mild steel surface.

In order to evaluate the influence of magnesium on the corrosion resistance of lead anodes in H2SO4 4 M, as well as on the microcrystalline morphology of lead, different electrochemical and metallurgical studies were made, such potentiodynamique polarization, electrochemical impedance spectroscopy, microhardness evolution, X-ray fluorescence spectroscopy and optical microscopy. The obtained results have shown that the addition of magnesium up to 1.5% in weight leads to a significant decrease in the corrosion current density (Icorr) and therefore, it increases the corrosion inhibition efficiency to 83% and it reduces the famous sulfation phenomena, by facilitating the transformation of PbSO4 and PbO to PbO2. It also makes the micro-structure of Pb much stronger, which makes the Pb anodes more resistant to mechanical shocks within the battery. We have also studied the effect of temperature on the corrosion of the new casting alloys. We found that an increase in temperature led to a decrease in its effect on the corrosion of alloys, compared with that of pure lead. Therefore, the new improved battery is more resistant, durable and more environment friendly.

In the present work, a simple and low-cost protocol for determination of gliclazide using modified screen-printed electrodes (SPE) was reported. The immobilization of magnetic core-shell manganese ferrite nanoparticles (MCSNP) onto SPE provides a unique opportunity for charge transfer process. Consequently, the electroanalytical sensing of gliclazide was explored at the modified SPE surface. The response of the modified electrode was linear, in the concentration range from 0.5 to 300.0 μM, and a detection limit of 100 nM was obtained. The proposed method was successfully employed for gliclazide determination in pharmaceutical and human urine samples. The method showed tremendous reproducibility and intra- and inter-day stability, and has proved to be highly reliable for gliclazide analysis in clinical samples.

Recently, there were reported investigations in the field of corrosion prevention, about finding effective environment-friendly alternative inhibitors, to replace toxic and harmful compounds. In the present review, the corrosion inhibition of some materials in various corrosive media, using imidazole derivatives, is summarized. Several organic compounds reported by many researchers are herein presented. This review considers previous studies conducted on various inhibitors, and provides an overview of some experimental techniques performed in order to investigate their corrosion properties.