The corrosion behaviour of AISI 347 in 0.1 M sulfuric acid at temperatures 50 and 75 °C and pressures up to 300 bar in a CO2 atmosphere was studied by surface analysis and electrochemical methods. ...Corrosion reactions in which CO2 is present accelerate the formation of a protective FeCO3 layer, but the success of such a passivation depends on the saturation concentration and the corresponding temperature. Significantly better results compared to untreated steels were obtained at lower temperatures by increasing the pressure. To explain the differences in corrosion rates between samples, the activation energy for the layer dissolution was also discussed. It can be assumed that the compressibility of the CO2 at different pressures has an influence on the formation of the protective iron carbonate layer and its properties and thus to on the corrosion behaviour.
The influence of heat treatment on AISI 420 in 0.1M H2SO4 was studied at passive potentials and increasing temperatures of acid, which lowers the passivity process and accelerates the dissolution of ...protective layers. Samples were compared with potentiodynamic measurements, EIS, SEM and EDS analysis. From Ea, Δ‡H∘andΔ‡S∘, further corrosive behaviour can be predicted in terms of the activation energy needed for the initiation of a chemical process on a metal surface: whether either passivation or dissolution of protective layer is preferred. In respect of those values, the passivity efficiency factor ηpass was introduced and represents best corrosion behaviour as it exceeds value 1.
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•On passive metal surfaces two main processes are present: passivation and dissolution of protective layers.•Values of activation energy, enthalpy of activation and entropy of activation were calculated.•From activation energies for both processes, the passivity efficiency factor has been introduced and shows best relationship for air quenched steel.•This result coincides with the EIS values.
A new rapid method has been developed for the determination of low levels of rosmarinic acid extracted from rosemary (Rosmarinus officinalis L.) and has been used as an antioxidant in meat and meat ...products after cold storage at 4°C. The method is a high performance liquid chromatography using a coulometric electrochemical detector. It provides a significant improvement on the limit of detection, which was 0.33 ppb, while the limit of quantification was 1 ppb of rosmarinic acid. The advantage of the method also lies in the simpler and faster sample preparation, which can quantify a very low concentration of rosmarinic acid (60 ppb), and is more than 40 ppb below the limits of previously existing methods. A coulometric method is well suited for determining low analyte concentrations and is one of the most sensitive analytical approaches available today, in addition to being time efficient and cost effective.
Practical Application
A new method for determining low concentrations (60 ppb) of rosmarinic acid in meat and meat products is presented. The method is user‐friendly, as it does not require complex sample preparation. It is a selective, precise, and accurate method that makes it useful for routine applications in the meat and other food industries.
•EIS was used to study film formation of three waterborne latex coatings.•Impedance of the coatings increased during film formation.•Warburg impedance was used to quantify particle deformation and ...coalescence.•AFM imaging showing particle deformation and coalescence confirmed EIS results.•EIS was shown to be suitable for studying latex film formation.
In order to establish electrochemical impedance spectroscopy (EIS) as a viable quantitative method for characterization of latex film formation, three waterborne acrylate and styrene–acrylate polymer dispersions were periodically analyzed during a course of 2 weeks. Impedance spectra were fitted on the base of equivalent circuit consisting of a capacitor in parallel with a Warburg element representing film capacitance and the extent of ion diffusion through the film. Calculated EIS parameter values showed a decrease in Warburg diffusion over time, which is a result of particle coalescence and in agreement with the established theory of latex film formation. Atomic force microscopy (AFM) of the samples showed a smoothing of the surface and blurring of interparticle boundaries which confirmed that EIS can be used to study film formation of latex.
Purpose - This paper aims to focus on the effects of temperature of the immersion media on the corrosion behaviour of differently heat-treated X20Cr13 stainless steel.Design methodology approach - ...Specimens, quenched on air, quenched in oil and quenched in oil and then tempered, were tested during exposure in 0.1 M H2SO4 at 30, 40 and 50°C. The results were interpreted on the base of potentiodynamic and impedance measurements.Findings - From the impedance spectra a reaction mechanism can be determined: after samples had reached and passed the active peak, expressed as the highest peak on the potentiodynamic curve, corrosion products at interfaces, which were adsorbed at metal surface, led to an increase in the charge transfer resistance. Elevated temperature of immersion media has had appreciable influence on the corrosion rate and adsorption of products, but at this temperature level did not affect the principle of corrosion reactions. Activation energies were calculated to exhibit temperature dependence of current density, which was the highest for the oil- and the lowest for the air-quenched sample.Originality value - The paper provides further research on stainless steel, the corrosion behaviour of which can be controlled already by heat treatment.
The structure of the porous aluminium-oxide layer, which builds non-image areas, has the most significant influence on the quality of final graphical product. This paper presents the results of the ...application of EIS in the characterisation and detection of changes on the aluminium-oxide layer caused by chemical processing in highly alkaline solution. The Al2O3 layer was characterised using SEM, fractal dimension and surface free energy calculation and EIS analysis. The results of the investigation showed that chemical processing has a significant influence on the structure of aluminium-oxide which could lead to a decrease in the quality of the printing plate. EIS enables the detection of changes on the aluminium-oxide layer. The two equivalent circuits are proposed. Based on modelling with the obtained EIS spectra, precise evaluation of developing time in which complete removal of the photoactive layer is achieved. This makes EIS a powerful tool in optimizing chemical processing of lithographic printing plates.
We monitored trends of severe COVID-19 morbidity in Slovenia during weeks 13 to 37 2021. National weekly rates of severe acute respiratory infections (SARI) cases testing positive for SARS-CoV-2 at ...admission in all hospitals varied between 0.2 and 16.3 cases per 100,000 population. Of those without previous COVID-19 diagnosis, SARI COVID-19 admission rates ranged between 0.3 and 17.5 per 100,000 unvaccinated, and 0.0 and 7.3 per 100,000 fully vaccinated individuals. National SARI COVID-19 surveillance is essential in informing COVID-19 response.
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