Electrochemistry of active chromium: Part II. Three hydrogen evolution reactions on chromium in sulfuric acid

It was shown that chromium in deaerated sulfuric acid exhibits two stable corrosion potentials, depending whether the metal had previously been in contact with air or subjected to activation by cathodically evolving hydrogen. Electrochemical polarization measurements, as well as measurements of the actual metal dissolution rate at the corrosion potentials, anodic or cathodic polarization, using the analytical determination of Cr ions in the solution, weight-loss of metal, or volumes of hydrogen evolved, showed that hydrogen can evolve on chromium by three different reaction mechanisms. The first one is the electrochemical hydrogen evolution reaction from H⁺ ions at the bare chromium surface obtained by cathodic activation. This reaction and the active anodic dissolution of chromium determine one stable corrosion potential. The second reaction is the reaction of H⁺ ions on the oxidized chromium surface which, coupled with the anodic dissolution of passivated chromium determines the other stable corrosion potential. The third one is the “anomalous” or chemical reaction of chromium with water molecules and hydrogen ions whereby hydrogen is liberated. This is a potential independent reaction, occurring on the bare metal surface, and which is at pH <2 several times faster at the corrosion potential than the electrochemical hydrogen evolution reaction. The consequence is that the overall corrosion rate is several times faster than that determined by the usual electrochemical methods. The applicability of the different methods of measuring electrochemical corrosion rates and cathodic current efficiencies in chromium plating is discussed. Also, a possible role of the “anomalous” chromium dissolution in corrosion fatigue and stress corrosion cracking of stainless steels is considered.     

Corrosion stability of polyester coatings on steel pretreated with different iron–phosphate coatings

The influence of steel surface pretreatment with different types of iron–phosphate coatings on the corrosion stability and adhesion characteristics of polyester coatings on steel was investigated. The phosphate coating was chemically deposited either from the simple novel plating bath, or with the addition of NaNO₂, as an accelerator in the plating bath. The morphology of phosphate coatings was investigated using atomic force microscopy (AFM). The corrosion stability of polyester coatings on steel pretreated by iron–phosphate coatings was investigated by electrochemical impedance spectroscopy (EIS) in 3% NaCl solution, while “dry” and “wet” adhesion were measured by a direct pull-off standardized procedure. It was shown that greater values of pore resistance, R_p, and smaller values of coating capacitance of polyester coating, C_c, on steel pretreated with iron–phosphate coating were obtained, as compared to polyester coating on steel phosphated with accelerator, and on the bare steel. The surface roughness of phosphate coating deposited on steel from the bath without accelerator is favorable in forming stronger bonds with polyester coating. Namely, the dry and wet adhesion measurements are in accordance with EIS measurements in 3% NaCl solution, i.e. lower adhesion values were obtained for polyester coating on steel phosphated with accelerator and on the bare steel, while the iron–phosphate pretreatment from the novel bath enhanced the adhesion of polyester coating on steel.     

Evaluating policy options for increasing the RES-E penetration in Greece

According to the current European and national legislation, Greece targets to a 40% share of renewable energy sources (RES) in electricity production by 2020.     

Randomized clinical trial of local anesthetic versus a combination of local anesthetic with self-hypnosis in the management of pediatric procedure-related pain.

A prospective controlled trial was conducted to compare the efficacy of an analgesic cream (eutectic mixture of local anesthetics, or EMLA) with a combination of EMLA with hypnosis in the relief of lumbar puncture-induced pain and anxiety in 45 pediatric cancer patients (age 6-16 years). The study also explored whether young patients can be taught and can use hypnosis independently as well as whether the therapeutic benefit depends on hypnotizability. Patients were randomized to 1 of 3 groups: local anesthetic, local anesthetic plus hypnosis, and local anesthetic plus attention. Results confirmed that patients in the local anesthetic plus hypnosis group reported less anticipatory anxiety and less procedure-related pain and anxiety and that they were rated as demonstrating less behavioral distress during the procedure. The level of hypnotizability was significantly associated with the magnitude of treatment benefit, and this benefit was maintained when patients used hypnosis independently. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cinnamic acid derivatives in cosmetics: current use and future prospects

Cinnamic acid derivatives are widely used in cosmetics and possess various functions. This group of compounds includes both naturally occurring and synthetic substances. On the basis of the Cosmetic Ingredient Database (CosIng) and available literature, this review summarizes their functions in cosmetics, including their physicochemical and biological properties as well as reported adverse effects. A perfuming function is typical of many derivatives of cinnamaldehyde, cinnamyl alcohol, dihydrocinnamyl alcohol and cinnamic acid itself; these substances are commonly used in cosmetics all over the world. Some of them show allergic and photoallergic potential, resulting in restrictions in maximum concentrations and/or a requirement to indicate the presence of some substances in the list of ingredients when their concentrations exceed certain fixed values in a cosmetic product. Another important function of cinnamic acid derivatives in cosmetics is UV protection. Ester derivatives such as ethylhexyl methoxycinnamate (octinoxate), isoamyl p‐methoxycinnamte (amiloxiate), octocrylene and cinoxate are used in cosmetics all over the world as UV filters. However, their maximum concentrations in cosmetic products are restricted due to their adverse effects, which include contact and a photocontact allergies, phototoxic contact dermatitis, contact dermatitis, estrogenic modulation and generation of reactive oxygen species. Other rarely utilized functions of cinnamic acid derivatives are as an antioxidant, in skin conditioning, hair conditioning, as a tonic and in antimicrobial activities. Moreover, some currently investigated natural and synthetic derivatives of cinnamic acid have shown skin lightening and anti‐ageing properties. Some of them may become new cosmetic ingredients in the future. In particular, 4‐hydroxycinnamic acid, which is currently indexed as a skin‐conditioning cosmetics ingredient, has been widely tested in vitro and in vivo as a new drug candidate for the treatment of hyperpigmentation.     

Adhesion characteristics and corrosion stability of epoxy coatings electrodeposited on phosphated hot-dip galvanized steel

The influence of hot-dip galvanized steel (HDG) surface pretreatment with phosphate coatings on the corrosion stability and adhesion characteristics of epoxy coatings electrodeposited on HDG steel was investigated. Phosphate coatings were deposited on hot-dip galvanized steel from baths with different concentrations of NaF (0.1, 0.5 and 1.0 g dm⁻³) and at different temperatures (50, 65 and 80 °C). The influence of fluoride ion concentration in the phosphating bath, as well as the deposition temperature of the bath, on the adhesion characteristics and corrosion stability of epoxy coatings on phosphated HDG steel was investigated. The dry and wet adhesions were measured by a direct pull-off standardized procedure, as well as indirectly by NMP test, while corrosion stability was investigated by electrochemical impedance spectroscopy (EIS).     

Phenolic Antioxidants in Cypriot Wines as a Tool for Their Varietal Discrimination： Preliminary Results

A total of 56 wines from different vintages and wine-growing regions of Cyprus were used to analyze six biologically interesting phenolic antioxidants （gallic acid, catechin, vanillic acid, epicatechin, coumaric and feroulic acid） by high performance liquid chromatography. The study includes red and white Cypriot authentic wines from local and imported varieties that were produced under the same vinification conditions at a Model Winery. Results extracted after the chemometric analysis of the measured concentrations show a strong relationship of the phenolic antioxidative capacity with the variety of the wines and gallic acid followed by vanillic acid found in the highest concentrations of the other antioxidants studied. Comparing the concentrations found with bibliographic data for wines from other countries, it was found that, the concentration levels of vanillic and ferulic acid were significantly higher for Cypriot wines.     

Corrosion rates and negative difference effects for Al and some Al alloys

The rotating disc-ring technique with a Pt ring was used to quantitatively detect hydrogen evolved on an Al-disc electrode during spontaneous corrosion at open-circuit potential or during anodic polarization of an Al disc to study the unusual increase of H2 evolution with increase in anodic current (the so called negative difference effect). Experiments were made with high purity Al (99.999%), technical grade Al (99.5%) (Al–T) and Al–In alloy (0.074% In) in deaerated 0.5m aqueous NaCl solution (pH6.5) and NaCl solutions acidified with HCl to pH values of 3.0, 2.0 and 1.0. It was shown, in neutral solutions, that the corrosion rates of all three materials are controlled by the rate of water molecule dissociation or in more acid solutions, by the combined water molecule dissociation rate and H+ ion discharge rate. The corrosion rates of all three materials in the range of 3–10Acm2, was the lowest for 99.999% Al. The impurities in Al–T and Al–In increase the hydrogen evolution rate at cathodic polarizations in a similar manner, but very differently affect the negative difference effect. High purity Al and Al–T have a similar negative difference effect (8–15%), while the presence of In decreases it to only about 1%. No pitting and no negative difference effect were observed at potentials more negative than Epit. Therefore, the negative difference effect is connected with the anodic pitting dissolution mechanism. Several aspects of this problem are discussed in more detail.