Portugaliae
Electrochimica Acta

In this paper, the performance of a composite particle for the deposition of ZnO/Cr2O3 on a zinc electrolyte was examined. Its susceptibility to corrosion in 3.5% NaCl, using linear polarization, was investigated. The developed crystal was characterized by using scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS). The strengthening properties of the coated samples, i.e. the mechanical response, were studied using a high sensitive diamond microhardness indenter and a MTR-300 rigid wear tester. From the results, the effect of the composite coatings interestingly influenced the performance regarding microhardness, durability, corrosion mitigation and wear damage. In general, the micro-hardness value for the Zn-ZnO material was 125.0 HVN, while it was 130.5 HVN for Zn-8ZnO-16Cr2O3 composite coating. For Zn-8ZnO-20Cr2O3, a better hardness performance was noted with 138.0 HVN. From the wear study, Zn-8ZnO shows 0.018 g/min dissociation against the counter body with the best wear performance obtained at 0.005 g/min. The corrosion properties of the developed composite coating also tend towards a more positive region, with a corrosion rate of 0.850 mm/yr. This shows that the role of composite particulates maximally contributes to improve the strengthening characteristics of the developed coating.

The adsorption capacity of activated carbon and activated carbon with amide group towards Ni(II), Zn(II) and Co(II) from aqueous solutions was studied in varying treatment conditions such as contact time, weight of sorbent, pH and initial concentration of treated metal ions. The adsorption capacity was investigated by batch experiments. The results showed that the removal percentages were enhanced by increasing the weight of the added sorbent, contact time, pH of the solution and the initial concentration of treated metal ions. The optimum order of increasing removal percentages of metal ions by using activated carbon (AC) prepared from sawdust of beech wood at pH=5, with an initial concentration of metal ions of 100 mg/L, and after two hours of shaking, was: Zn(II)

This study reports the evaluation of the anticorrosive performance of polymer epoxy resin, namely, Diglycidyl ether 4, 4’-dihydroxydiphenylsulfone (DGEDDS) and its polymer composite reinforced with Titanium Dioxide (TiO2), for carbon steel (CS) corrosion, in 3% wt. NaCl, using experimental analyses. Thermal, electrochemical and morphological techniques were used to demonstrate the anticorrosive effectiveness of the standard epoxy resin (MP1) and its TiO2 composite (MP2). The effect of UV irradiation (for 2000 h), on the effectiveness of MP1 and its TiO2 composite (MP2), showed that TiO2 presence appreciably enhanced the protection efficiency effect of MP1.

The corrosion inhibition property of Gymneme Sylvestre on aluminum in an acidic medium has been investigated. The experimental techniques include potentiodynamic polarization studies, electrochemical studies, quantum chemical calculation and weight loss method. The results revealed that Gymneme Sylvestre acts as a potential corrosion inhibitor of aluminum in an acidic medium, showing 82% inhibition efficiency at 800 ppm concentration of it. Furthermore, the different thermodynamic parameters, including activation energy, Gibbs free energy and enthalpy have been calculated. The results showed that adsorption of the Gymneme Sylvestre molecule onto the aluminum coupon surface obeys Langmuir adsorption isotherm. The quantum chemical parameters were also calculated for major constituents of Gymneme Sylvestre.

Carbon steel corrosion inhibition in a hydrochloric acid solution by 2-[(5-methyl-isoxazol-3-yl)-methyl]-benzimidazole (MMB) has been studied by electrochemical techniques (PDP and EIS). Results showed that the inhibition efficiency increases with higher MMB concentration, and the maximum value of 86.6% was obtained at 10-3 M concentration. The prepared benzimidazole inhibitor showed higher inhibition efficiency upon raising the solution temperature from 303 to 333 K. Corrosion current density decreased from 660.9 µA cm-2 (blank) to 97.8 µA cm-2 (MMB) and charge transfer resistance increased from 20.2 Ω cm2 (blank) to 150.8 Ω cm2 (MMB). PDP studies showed that MMB is a mixed type inhibitor. The adsorption of this compound onto the carbon steel surface in a 1 M HCl solution followed the Langmuir adsorption isotherm, and the value of the standard free energy of adsorption ( ) is associated to physisorption and chemisorption.