I .. Rates of ionic mass transfer at nickel electrodes rotating about their axes In the center of stationary electrodes were studied using the ferri-ferrocyanide oouple In alkaline solutions. A general mass transfer correlation was found to apply equally well to the dissolution rates of rotating solids and to the rates of ionlo mass transfer at rotating electrodes. This correlation takes into account the physioal properties of the system as well as geometric and hydro dynamic factors. The correlation enables the prediction of limiting currents and concentration polarisation at rotating electrodes under a wide range of conditions. The nature of the polarisation involved in the reduotion of Fe(CNfe~» and the oxidation of Fe(CN#* was also Investigated. The polarisation was found to depend strongly on the presence of "electrode poisons." With freshly prepared solutions, under exclusion of light and with eathodlcally treated nickel electrodes relatively small ehesdcal polarisations were determined. For rotational speeds not exceeding Reynolds number 11,000, the chemical polarisation was found to be negligicle in comparison with the concentration polarisation* Under such conditions the ferro-ferrioyanide oouple can be conveniently used to obtain mass transfer rates for various hydrodynamic conditions, or, conversely, to verify the validity of mass transfer equations by a comparison of experimental .and calculated values of limiting currents and concentration polarisation. The rotating electrode model was found to be most suitable for studying the nature of eleotrolytio polarisation phenomena on aocount of the uniformity of the current distribution as well as of the hydrodynamio diffusion laver at the electrode surfsee.

Mass transfer in electrode processes. 3. ionic mass transfer and concentration polarization at rotating electrodes

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The Science And Engineering Of Materials

Effect of stereochemical conformation into the corrosion inhibitive behaviour of double azomethine based Schiff bases on mild steel surface in 1 mol L−1 HCl medium: An experimental, density functional theory and molecular dynamics simulation study

Inspired by the water-collecting mechanism of the Stenocara beetle’s back structure, we prepared a superhydrophilic bumps–superhydrophobic/superoleophilic stainless steel mesh (SBS-SSM) filter via a facile and environmentally friendly method. Specifically, hydrophilic silica microparticles are assembled on the as-cleaned stainless steel mesh surface, followed by further spin-coating with a fluoropolymer/SiO2 nanoparticle solution. On the special surface of SBS-SSM, attributed to the steep surface energy gradient, the superhydrophilic bumps (hydrophilic silica microparticles) are able to capture emulsified water droplets and collect water from the emulsion even when their size is smaller than the pore size of the stainless steel mesh. The oil portion of the water-in-oil emulsion therefore permeates through pores of the superhydrophobic/superoleophilic mesh coating freely and gets purified. We demonstrated an oil recovery purity up to 99.95 wt % for surfactant-stabilized water-in-oil emulsions on the biomim...

Inspired by Stenocara Beetles: From Water Collection to High-Efficiency Water-in-Oil Emulsion Separation

The oxidation processes of Fe(II) hydroxo-complexes to α-, β-, γ-, and δ-FeOOH and Fe3O4, which are important atmospheric products of steels, and the effect of Cu2+, PO43− ion on the oxidation of the Fe(II) hydroxo-complexes in aqueous solutions have been investigated. The mechanism of atmospheric rusting deduced from the results obtained in the present investigation has been used to explain the difference in behaviour between ordinary mild steels and low alloy steels during atmospheric exposure. It is concluded that Fe(II) complexes are transformed to amorphous δ-FeOOH by the catalytic effect of Cu and P present in steels. The amorphous δ-FeOOH forms a compact rust layer that enhances corrosion resistance of the steel.

The Mechanism of Atmospheric Rusting and the Effect of Cu and P on the Rust Formation of Low Alloy Steels

The purpose of this paper is to analyze the main issues concerned with the oxidative and storage stabilities of biodiesel and how they affect different metallic and polymeric materials present in automotive parts and in biodiesel storage structures. In addition, this work presents a review of the techniques used for measuring the oxidative stability and for evaluating the degradation of metallic and polymeric materials. When biodiesel is oxidized, a series of changes in its properties occurs. These changes not only affect biodiesel quality, but also the properties of the materials that are in contact with it. Upon oxidation, biodiesel properties like the acid value, peroxide value and viscosity increase, while the iodine value and the content of methyl esters decrease. The changes in the chemical and physical properties of biodiesel can affect the integrity and stability of the material. The situation reviewed in this paper, which talks about the stability of materials, could limit the extensive use of biodiesel. Such measures have been proposed in several countries, and it is a topic of great importance for biodiesel technology.

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The oxidative stability of biodiesel and its impact on the deterioration of metallic and polymeric materials: a review

In this paper the effect of current density and anodizing potential on both surface morphology and internal structure of Ti anodic coatings were studied. Anodic films were obtained in galvanostatic and potentiostatic modes. Anodic films obtained at galvanostatic mode do not show significant changes in surface morphology, exhibiting a porous structure of circular pores. Nevertheless, the anodic films obtained at potentiostatic mode show two different morphologies depending of the potential applied. The chemical composition of the coatings assessed by micro-Raman spectroscopy shows that the coatings are composed mainly of titanium dioxide in anatase phase with presence of some constituents of the anodizing solution as evidenced by EDS. Furthermore, EIS analysis allowed to correlate internal structure changes in the coatings with changes in the electrical parameters of the layers forming the coating.

Effect of electrochemical parameters on the formation of anodic films on commercially pure titanium by plasma electrolytic oxidation

http://sites.poli.usp.br/org/emcr2012/CD/PDF/Poster/Tu-02_Bedoya.pdf

Erosion–corrosion resistance of Ni composite coatings with embedded SiC nanoparticles

Aggressiveness of a 20% bioethanol–80% gasoline mixture on autoparts: I behavior of metallic materials and evaluation of their electrochemical properties

In this study, Ni-P/Ni(OH) 2 -ceramic nanoparticle composite coatings were directly deposited onto commercially pure magnesium in order to improve its resistance to erosion-corrosion damage. The effect of three incorporated ceramic nanoparticles (TiO 2 , SiC and diamond) on the erosion-corrosion resistance of the composite coatings was also investigated. The composite coatings were obtained by an electroless process and were characterized using scanning electron microscopy, Raman spectroscopy and X-ray diffraction. The erosion-corrosion behavior of fabricated composite coatings was elucidated using in situ techniques of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). It was found that the simultaneous formation of Ni-P and β-Ni(OH) 2 phases in the coating and the improvement in the micro hardness of the coating were due to the incorporation of nanoparticles. According to the polarization curves and EIS spectra, the β-Ni(OH) 2 compound behaves like a pre-passive film which is responsible for substantial improvement in the anticorrosion properties of the coating. Better erosion-corrosion resistance was obtained for the composite coatings than the neat Ni-P coating. This was a consequence of the β-Ni(OH) 2 co-deposition. The formation of the β-Ni(OH) 2 compound in the coating does not depend on the nature and concentration of the nanoparticles.

Jorge A. Calderón

Papers

The oxidative stability of biodiesel and its impact on the deterioration of metallic and polymeric materials: a review

Effect of electrochemical parameters on the formation of anodic films on commercially pure titanium by plasma electrolytic oxidation

Erosion–corrosion resistance of Ni composite coatings with embedded SiC nanoparticles

Aggressiveness of a 20% bioethanol–80% gasoline mixture on autoparts: I behavior of metallic materials and evaluation of their electrochemical properties

Improvement of the erosion-corrosion resistance of magnesium by electroless Ni-P/Ni(OH)2-ceramic nanoparticle composite coatings