Portugaliae
Electrochimica Acta

Natural oil extracted from apricot seeds was evaluated as carbon steel corrosion inhibitor in 1 M hydrochloric acid, using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and weight loss measurements. The measurements show that apricot seed oil is a good inhibitor for carbon steel corrosion in a hydrochloric environment, and this inhibitive action was mainly due to its adsorption onto the carbon steel surface, and active sites blocking. The above results showed that apricot seed oil acted as a mixed-type corrosion inhibitor, and that its adsorption onto the carbon steel surface obeyed the Langmuir adsorption isotherm. The inhibition effectiveness increased with the inhibitor concentration, and reached 83.49% at 0.5 g/L, in a 1 M HCl medium. Some thermodynamic parameters of the studied inhibitor were calculated and discussed.

Surface laser treatments of commercially pure titanium plates (CP-Ti grade 4) were performed in air using a Nd:YAG laser source of short pulse duration about 5 ns. Attention is drawn to the following laser-processing parameters: laser-power interaction time and surface of the irradiated zone. The morphology, structure and chemical composition of the formed layers were analyzed by different characterization techniques providing physico-chemical and structure information. The objective of this research was to study the influence of laser fluence on the composition of the CP-Ti grade 4. Additionally, it was pretended to evaluate the surface modification of obtained layers. The electrochemical response of modified surface in Ringer’s physiological solutions at varying pH values was studied. Fretting test has been investigated in order to study the tribological behavior of the laser treated surface. Results showed that the laser treatments induce the insertion of light elements such as O2 and N2. Laser surface processing shifted the corrosion potential of CP-Ti grade 4 towards the noble side, as compared to the untreated one. After fretting tests, it was found that the steady friction coefficient was similar for all the layers, and quite lower than that measured for the untreated CP-Ti.

This work reports the development of a glassy carbon electrode (GCE), modified with an oxidized poly diphenylamine/multi-walled carbon nanotubes-β-cyclodextrin (OPDPA /MWCNT-β-CD) composite film, for ceftazidime determination. The OPDPA/MWCNT-β-CD film surface morphology was investigated using field emission scanning electron microscopy (FESEM) and cyclic voltammetry (CV). Ceftazidime was adsorbed onto the OPDPA/MWCNT-β-CD, at open circuit, for 240 seconds, and then oxidized in acidic media. The electrochemistry of ceftazidime oxidation was investigated using cyclic voltammetry and differential pulse voltammetry (DPV). Under optimum conditions, the peak current linearly increased with ceftazidime concentration, in the range of 5×10-8 M to 1×10-5 M. The obtained detection limit was 1.0×10-9 M. This sensor was employed for ceftazidime determination in the biological and pharmaceutical samples.

A comparative study of the corrosion behavior of pure magnesium and AZ91D anodes in reinforced cement concrete was undertaken in the present work. The steel reinforcements were electrochemically kept in contact with these anodes in a chloride atmosphere, and the half-cell potential drop was observed. Bare steel reinforcements were tied to the anodes and were also kept in a high chloride atmosphere to test the mechanical properties. The yield stress and ultimate tensile stress were found to decrease by approximately 50 MPa, while the reduction in percentage elongation was approximately 25% for reinforcements tied to AZ91D and pure Mg, at the end of 80 days, compared to the fresh steel reinforcement. The rate of corrosion of pure Mg was reportedly slightly higher compared to AZ91D, due to the presence of inter-metallics, as inferred through micro-graphs.

New corrosion inhibitors of benzimidazole derivatives, namely: 6-methoxy-2-(((4-methoxy-3,5-dimethylpyridin-2-yl)methyl)sulfinyl)-1-vinyl-1H-benzo[d]imidazole (EMSB), 6-Methoxy-2-(((4-methoxy-3,5-dimethylpyridin-2-yl)methyl)) sulfinyl)-1-(prop-2-yn-1-yl)-1H benzimidazole (MSVB) and 6-methoxy-2-(((4-methoxy-3,5-dimethylpyridin-2-yl)methyl)sulfinyl)-1-(phenacyl)-1-H benzimidazole (MSBP), have been synthesized and their inhibiting action on the corrosion of carbon steel in acidic bath (1 M HCl) has been investigated by various corrosion monitoring techniques, such as weight loss measurement, potentiodynamic polarization, adsorption, electrochemical impedance spectroscopy (EIS) and basic computational calculations. The results of the investigation show that the inhibition efficiency of all the three inhibitors increases with increase in concentration of inhibitors and decreases with increase in temperature. The inhibitors, MSBP, MSVP, and EMSB show corrosion inhibition efficiency of 98, 97 and 93% respectively, at 10-3 M and 303 K. EIS measurements showed an increase of the transfer resistance with the inhibitors concentration. Polarization studies showed that the studied inhibitors are mixed type in nature and the adsorption of benzimidazole is described by the Langmuir isotherm. In addition, density functional theory (DFT) calculations and molecular dynamics simulations (MDS) were undertaken to describe the electronic and adsorption properties of the synthesized inhibitors constituents, including the synergistic/dispersive interactive effects of the multiple adsorptions of the various active constituents in the inhibitor film on the iron surface. Also DFT and Molecular dynamic (MD) simulations were employed to correlate the experimental findings.