H2 Gas Evolution Research Articles

Eco‐friendly corrosion inhibitors: the inhibitive action of Delonix Regia extract for the corrosion of aluminium in acidic media

PurposeTo investigate the inhibitive effect of Delonix regia extracts to reduce the corrosion rate of aluminium in acidic media. The study was a trial to find a low cost and environmentally safe inhibitor to reduce the corrosion rate of aluminium.Design/methodology/approachThe inhibition efficiency was evaluated using the hydrogen evolution technique at 30°C. The mechanism of adsorption inhibition and type of adsorption isotherm was characterised from trends of inhibition efficiency and kinetic data.FindingsDelonix regia extracts inhibited the corrosion of aluminium in hydrochloric acid solutions. The inhibition efficiency increased with increasing concentration of the inhibitor but decreased with increase in exposure time. The acid extracts (hydrochloric acid seeds extract (HSE) and hydrochloric acid leaf extract (HLE)) were found to be more effective than the ethanolic extracts (ethanol seeds extract (ASE) and ethanol leaves extract (ALE)) and the inhibition followed the order: HSE (93.6 per cent) > HLE (83.5 per cent) > ASE (63.9 per cent) > ALE (60.4 per cent). The low negative values of ΔGad: −20.14 kJ mol−1 for HSE, −18.08 kJ mol−1 for HLE, −15.96 kJ mol−1 for ASE and −15.12 kJ mol−1 for ALE, as calculated from the Langmuir isotherm, indicated that the inhibitor molecules adsorbed onto aluminium by a physiosorption‐based mechanism. A first‐order type of reaction mechanism was obtained from the kinetic treatment of the H2 gas evolution data.Research limitations/implicationsFurther investigations involving electrochemical studies such as polarization method should shed further light on the mechanistic aspects of the corrosion inhibition.Originality/valueThis paper provides new information on the possible application of Delonix regia as an environmentally friendly corrosion inhibitor under the specified conditions. This environmentally friendly inhibitor could find possible applications in metal surface anodizing and surface coatings.

Exfoliation and Restacking Route to Anatase-Layered Titanate Nanohybrid with Enhanced Photocatalytic Activity

A new microporous TiO2-pillared layered titanate has been prepared by hybridizing the exfoliated titanate with the anatase TiO2 nanosol. The stable colloidal nano-sheet was obtained by intercalating tetrabutylamine into the layered protonic titanate, HxTi2-x/4□x/4O4·H2O (x = 0.67), with a lepidocrocite-like structure. The colloidal suspension of exfoliated titanate sheets was mixed with the monodispersed anatase TiO2 nanosol solution prepared by the hydrolysis of titanium isopropoxide with acetylacetone. The obtained nanohybrid was heated at 300 °C for 2 h in order to complete the grafting reaction of intercalated anatase TiO2 nanosol on the interlayer surface of layered titanate. According to the X-ray diffraction analysis and N2 adsorption−desorption isotherms, it was found that the TiO2-pillared layered titanate showed a pillar height of ∼2 nm, a high surface area of ∼460 m2/g, and a pore size of ∼0.95 nm, indicating the formation of a microporous pillar structure. Its photocatalytic activity was evaluated by measuring the total volume of H2 gas evolved during the irradiation of the catalyst suspensions in water. The H2 gas evolution was found to increase from the layered titanate (cesium and protonic form) to the unsupported TiO2 (acac-TiO2) and the TiO2-pillared layered titanate, because the electron and hole recombination in the pillared system is thought to be effectively suppressed because of electron transfer between guest and host. A marked enhancement in the activity by ca. 40 times was obtained for TiO2-pillared layered titanate compared to pristine compounds such as layered titanate and anatase TiO2 nanosol when Pt (0.3 wt %) was doped on the surface of the sample.

硝酸水溶液中での電気化学的処理によるアルミニウム表面のFeAl<SUB>3</SUB>の選択除去

It is well-known that iron is one of the most common impurity elements observed in industrial aluminum. Iron in the aluminum forms an intermetallic compound such as FeAl3. The FeAl3 exposed on the aluminum matrix are detrimental to corrosion. A simple and effective electrochemical treatment, by which selective removal of FeAl3 can proceed, has been developed with a number of trials. It is found that FeAl3-free surface is obtained by electrochemical treatments in a 17 mass%HNO3 solution. It is explained that a selective removal by electrochemical treatment attributes to two operations; one is the activation of FeAl3 surface by H2, N2O, NO and NO2 gas evolution reactions, and the other is the cathodic reactions:(This article is not displayable. Please see full text pdf.)

Electrodeposition of rhodium. Part 1. Chloride solutions

The electrodeposition of rhodium metal from 1 M NaCl + HCl, pH 1.5 to 4, has been investigated. It is demonstrated that, although the Rh(III) exists as a mixture of aquo/chloro complexes, only a single, steep reduction peak is observed for the reaction Rh(III) → Rh and the response corresponds to reduction of all the Rh(III) in solution. Hydrogen adsorption and H2 gas evolution occur readily on the freshly deposited Rh surface. Good quality electroplates are formed on vitreous carbon and it is confirmed that the inferior quality plates on Cu and steel result from a slow chemical reaction between the metals and Rh(III) in chloride solutions.

Gas-liquid turbulent two phase flow along vertical flat plate with gas evolution.

Gas-liquid turbulent two phase flow along a vertical flat plate with gas evolution was numerically simulated with a two-fluid model and Plandtl’s mixing length theory using the SIMPLER method. The calculation domain was assumed to be two-dimensional and gas bubbles to be evolved uniformly from the plate surface. The computed velocity profiles were affected by void fraction on the wall and the bubble diameters, but not by the bubble departure velocity from the plate surface. Both the gas and liquid velocity profiles and the computed wall shear stress with the present model were qualitatively and quantitatively coincident with those measured using LDV for the vertical flat plate electrode with H2 or O2 gas evolution.

高ケイ素含有鋼の溶融亜鉛めっきにおける異常付着とその防止方法

Abnormal Deposition with an irregular surface and an abnormally thick structure involving many cavities was obtained on high silicon steel having both an ordinary surface scale (Fe3O4 and α-Fe), and a subscale with fayalite (2FeO·SiO2). In abnormal deposition H2 gas evolved in large amounts during pickling, leaving a residual subscale on the steel surface, and that, in hot dip galvanizing, H2 gas released from the residual subscale was arrested in the deposits and ξ-phase precipitated directly and rapidly on the steel surface through cracks in the δ-phase layer induced by H2 gas evolution. It was found that abnormal deposition could be prevented by: 1. Completely removing subscale by pickling. 2. Descaling by a mechanical method, without H2 gas evolution. 3. Baking if residual subscale is still present after pickling.

Fermentative metabolism of pyruvate by Rhodospirillum rubrum after anaerobic growth in darkness

Rhodospirillum rubrum grew anaerobically in darkness and fermented sodium pyruvate by a pyruvate formate-lyase reaction. During 30 min of anaerobic dark or light incubation with sodium pyrivate, crude extracts from fermentatively grown cells produced about 6 micronmol of acetylphosphate and formate per mg of protein in reactions performed at pH 8.3. Cell extracts also catalyzed the exchange of sodium [14C]formate into sodium pyruvate at an apparent pH optimum of 7.3 to 7.5, but only about 2.5 micronmol of acetylphosphate was produced at this lower pH value. R. rubrum may also form pyruvate:ferredoxin oxidoreductase activity, as evidenced by low bicarbonate exchange activity. However, its participation in pyruvate metabolism in anaerobic dark-grown cells was not understood. During anaerobic, dark growth with pyruvate, formate was an intermediate in H2 and CO2 gas evolution. In contrast with H2 production by a light-dependent H2-nitrogenase system in photosynthetically grown cells, H2 formation in fermenting R. rubrum occurred through a carbon monoxide-sensitive formic hydrogenlyase reaction not influenced by light.