Rotating Cylinder Electrode System Research Articles

Preparation of Co-S/NixSey/C@TiO2 composite electrode and the performance improvement strategies for the electrooxidation of H2O2

BackgroundThe cleanliness and ease of storage and transportation of H2O2 make it a promising fuel of fuel cell, but improving the catalytic activity of H2O2 electrooxidation is a prerequisite. MethodThe Co-S/NixSey/C@TiO2 electrode was prepared by “vapor deposition” and “two-step electrodeposition”, and the electrode was scaled up and fabricated into a rotating cylinder electrode to improve the catalytic performance of H2O2 electrooxidation. Significant findingsThe presence of Se-Se bonds and the synergistic effect of Co-S compound and NixSey gave the electrode a reduced oxidation potential for the electrooxidation of H2O2. The three-dimensional (3D) structure of the electrode facilitated the exposure of the catalyst active site, and the loading of Co-S compound improved the hydrophilicity of electrode. It's important to note that an original rotating cylinder electrode system was fabricated using an enlarged Co-S/NixSey/C@TiO2 electrode to weaken concentration polarization and reduce bubble adsorption on the electrode surface. Through the study, rotation of electrode and circulation of reaction solution exhibit positive effect for the electrooxidation reaction. Especially with a rotation speed of 37 r min−1 of electrode, the performance was improved by 85%. This study provides new strategies for improving the performance of H2O2 electrooxidation, which is of high research significance.

Flow Accelerated Corrosion of Carbon Steel with Droplet Impingement Using a Modified Rotating Cylinder Electrode Experiment

In power plant cooling systems, water droplets and condensate films form due to heat transfer through cooling tube walls. Condensate films are known to cause flow accelerated corrosion on carbon steels used in air-cooled condensers. Corrosion is further accelerated by droplets suspended in the accelerating steam that impinge on walls, T-joints, or valves, further damaging protective oxide layers on pipe walls. Droplet impingement and flow accelerated corrosion were studied using a modified rotating cylinder electrode system coupled with electrochemical impedance spectroscopy. Surface liquid films caused by droplet impingement were found to correlate directly with flow accelerated corrosion caused by condensate films. In the absence of a stable liquid film, droplet impingement increased corrosion rates and resulted in pit formation. Select corrosion inhibitors were found to be ineffective under flow accelerated corrosion or droplet impingement.

Exploring the sintering process parameters on erosion-corrosion characteristics of Fe-Cr-Ni steels in artificial mine water

Abstract This study investigates the erosion-corrosion behaviour of spark plasma sintered Fe-Cr-Ni relating additive and synergistic effects on the sintering temperature and time in mining and mineral processing industries. All tests were carried out using a rotating cylinder electrode system. The relative density has a relationship with the hardness values of the sintered alloys. The results linked the effects of the stainless steel sintering parameters (temperature and time) on the total mass loss, pure erosion, erosion-enhanced corrosion, and corrosion-enhanced erosion conditions. No correlation exists between the erosion-corrosion components and the densification mechanism since the porosity of the samples does not influence the sintered alloys behaviour. The surfaces indicated localized attack which increased with increasing time but decreased as the sintering temperature increased.

Evolution of the Corrosion Product Film and Its Effect on the Erosion–Corrosion Behavior of Two Commercial 90Cu–10Ni Tubes in Seawater

The composition and structural evolution of the corrosion product film of two commercial 90Cu–10Ni tubes, namely Tube A and Tube B, after being immersed in natural seawater for 1, 3, and 6 months were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, and its effect on the erosion–corrosion behavior of the tubes was determined through a rotating cylinder electrode system using various electrochemical techniques. For the freshly polished samples used as contrast samples, the flow velocity mainly enhanced the cathodic reaction at low flow velocities while both the anodic and the cathodic reactions were remarkably accelerated at higher flow velocities. The corrosion product films formed on the two commercial 90Cu–10Ni tubes after being immersed in seawater for up to 6 months are of a complex three-layer or multilayer structure. The structural evolution of the films is out of sync for the two tubes. A continuous residual substrate layer depleted of Ni was observed in the inner layer of the films on Tube B after 30, 90, and 180 days’ immersion, while it was observed in the film on Tube A only after 180 days’ immersion. The nature of the inner layer plays a crucial role in the erosion–corrosion resistance of the 90Cu–10Ni tubes at higher flow velocity. The film with a compact and continuous inner layer of Cu2O doped with Ni2+ and Ni3+ which bonds firmly with the substrate could survive and even get repaired with the increased flow velocity. The film on Tube B possessing a hollow and discontinuous inner layer composed of the residual substrate was degraded rapidly with increasing rotation speed in spite of its quite good resistance at the stagnant or lower speed conditions.

Influence of Shear Stress on Erosion–Corrosion of Stainless Steels in Simulated Mine Water

This study provides information on the performance of three stainless steels at various shear stresses and presence of silica sand particles in simulated mine water. The materials employed were two duplex stainless steels (UNS S32205 and UNS S32750) and one austenitic stainless steel (UNS 30403). The rotating cylinder electrode system produced shear stresses to evaluate the flow-induced and erosion–corrosion tests by open-circuit potential and potentiodynamic polarization techniques. Hardness tests were used to examine the performance of the degraded samples, and scanning electron microscopy was used to characterize the surface morphology. UNS S32750 displayed nobler OCP compared with UNS S32205 with austenitic steel having the least potential irrespective of the shear stresses and with/without silica sand. Work hardening of the duplex stainless steels promoted variable behavior in the hardness results. The current density results revealed that UNS S32705 had the best corrosion performance in the studied environments. The SEM images showed plastic deformation, material dissolution and pitting corrosion as the shear stress increased and on the introduction of silica sand.

Erosion-corrosion characteristics of spark plasma sintered pure nickel in simulated mine water

This study estimates the impact of shear stress and solid particles on the erosion-corrosion behaviour of spark plasma sintered pure nickel in simulated mine water. Rotating cylinder electrode system was employed to carry out the erosion-corrosion tests by weight-loss and electrochemical measurements. Corroded coupons were examined with the aid of microscope to assess the surface morphology. The gravimetry data was inconsistent with both weight gain and weight loss recorded. The impact of the hydrodynamic parameters was correlated with the pitting resistance and re-passivation behaviour of the sintered nickel, while the morphology results showed minimal general attack and severe localised corrosion.

Impact of solution hydrodynamics on the deposition of CaSO4 on brass

ABSTRACT An investigation was conducted to study the impact of solution hydrodynamics on the deposition of calcium sulfate scale on commercial brass by using a rotating cylinder electrode system at various pre-set rotational speeds, at 60 and 70°C on 120 and 600 grits polished cylindrical specimens. The effects of temperature, surface roughness, and flow conditions on the deposition of calcium sulfate scale on brass are presented. The results indicate the influence of solution hydrodynamics on the rate of calcium sulfate scale deposition on brass specimens by delineating the competing effect between the scale deposition and scale removal process that is occurring simultaneously under the fluid flow conditions generated in the study. The morphology of deposited crystals was obtained from scanning electron microscope (SEM) micrographs and composition was determined with energy dispersive X-ray spectrometer (EDS) method. The SEM analysis revealed prismatic needle- and rod-like crystals growth structure at nu...

Interaction of mechanical and electrochemical factors in erosion–corrosion of carbon steel

The interaction of mechanical and electrochemical factors in the erosion–corrosion process of carbon steel A1045 was investigated in Na 2SO 4 solution/silica sand slurry with a rotating cylinder electrode system. In line with the mechanism associated with material wastage, the synergism due to the interaction of erosion and corrosion was divided into corrosion-enhanced erosion and erosion-enhanced corrosion. The electrochemical experimental results indicated that the carbon steel showed active dissolution behavior, and the corrosion process was not controlled by the mass transfer when the rotating velocity is high enough. Scratching electrode tests and tensile tests were conducted to simulate the effect of sand impingement on corrosion process. Results showed that the impingement of the solid did not affect the corrosion behavior significantly in the present system. For the effect of corrosion on erosion, a half-logarithm relationship was found between weight loss due to corrosion-enhanced erosion and the applied anodic current density. According to a chemo-mechanical model, this effect can be attributed to the hardness degradation in metal surface with corrosion current.

Erosion–corrosion of chromium steel in a rotating cylinder electrode system: some comments on particle size effects

The effect of particle size on the erosion–corrosion response of a Cr containing steel in NaOH was studied in a rotating cylinder electrode system. The results showed that for the same addition of particles by weight, the corrosion rate in the presence of erosion was independent of particle size. However, the erosion–corrosion rate appeared to be dependent on particle sizes for size ranges from 50 to 100 μm but above this value, this dependence was reduced. Erosion–corrosion mechanism and wastage maps were constructed based on the results showing the variation in erosion–corrosion regimes, as a function of particle size and electrochemical potential.

The Inhibitive Characteristics of Mixed Inhibitor Combinations Under Heat and Mass Transfer Conditions

Oil and gas production operations are characterized by the inevitability of numerous technical problems related to the nature of the products and effluents. Moreover, these problems change gradually and require a periodic adjustment of the solution. One of the major concerns in the oil and gas industry is corrosion. Corrosion can be defined as the destruction or deterioration of material because of a reaction with its environment. In this paper the inhibitive characteristics of mixed inhibitor combinations on mild steel, under controlled conditions of heat and mass transfer, have been investigated using a rotating cylinder electrode system. Potentiostatic polarization experiments were carried out in both inhibited and uninhibited brackish water solutions under isothermal and heat transfer conditions. The optimum concentrations of the inhibitors used were estimated under the isothermal and dynamic conditions. Under isothermal conditions, the limiting current density values of oxygen reduction in the brackish water followed the Eisenberg equation. The presence of heat transfer enhanced the oxygen transfer rate over and above the value under isothermal conditions. The corrosion potential, passivation potential, and passive current density values, were a complex function of temperature, flow rate, and heat transfer. The anodic current density values increased with increases in temperature, flow rate, and the presence of heat transfer. The mixed inhibitor combinations showed high protection efficiency under the studied heat and mass transfer conditions.

Effects of erosion on corrosion of type 430 and 316 stainless steels in aqueous environments

The effects of erosion on the corrosion of two types of stainless steel in aqueous 0·5M NaCl and 1M NaCl environments at ambient temperature have been studied using a modified rotating cylinder electrode system. Erosion by silica particles greatly increased the passive current density for both ferritic type 430 and austenitic type 316 stainless steels. It is suggested that two factors were largely responsible for the observed effects. The impact of the eroding silica particles on the specimen surface destroyed the passive film and removed corrosion products from the specimen surface; and impact with the fast moving silica particles generated numerous microplastic deformation sites on the metal surface which were activated owing to the presence of residual stress, dislocations and defects, etc., and the emission of low energy electrons.

Erosion- and wear-corrosion behavior of Fe–Mn–Al alloys in NaCl solution

The erosion- and wear-corrosion behavior of solution-annealed and age-treated Fe–Mn–Al alloys in aerated 3% NaCl solution were investigated using a self-made rotating cylinder electrode system. The results showed that the open circuit potentials of Fe–Mn–Al alloys in 3% NaCl solution increased with increasing rotation speed during the erosion-corrosion test, but decreased with increasing rotation speed and contact load during the wear-corrosion test. Potentiodynamic polarization curves showed that the Fe–Mn–Al alloys had no passive region during erosion- and wear-corrosion tests, except that the solution-annealed specimen had an active-to-passive transition behavior during the erosion-corrosion test. After potentiodynamic polarization curve measurements during erosion- and wear-corrosion tests, the ferrite phase in solution-annealed Fe–Mn–Al alloy was prone to corrode with respect to the austenite phase. However, for age-treated Fe–Mn–Al alloy, corrosion preferentially occurred in the austenite phase region where β-Mn precipitated.

Corrosion of PVD TiN coatings under simultaneous erosion in sodium carbonate/bicarbonate buffered slurries

The aqueous corrosion resistance of mild steel (BS6323) in the presence and absence of PVD TiN coatings was studied potentiodynamically in a rotating cylinder electrode system, in comparison with that of AISI 304 stainless steel, in an alkaline buffer slurry solution of sodium carbonate and bicarbonate containing 150 μm alumina particles at a velocity up to 8 m/s. Weight loss of the samples resulted due to the action of both wear and corrosion. This paper summarises the preliminary results for studies of corrosion of the coated and uncoated samples. In addition, the weight loss due to corrosion under conditions of simultaneous erosion–corrosion was obtained from the current response using Faraday's law. The significant resistance to corrosion and the outstanding stability of the corrosion resistance with the increases of particle velocity accounted for the excellent corrosion performance of the TiN coatings over that of AISI 304 stainless steel or the mild steel.

Prediction of Product-Selectivity in an Electroorganic Process by Mathematical Modeling of Reaction Mechanism. A Rotating Cylinder Electrode System

Abstract A mathematical mechanism model is developed for the electroreduction of carbonyl compounds in an acidic solution and shows that the formation ratio of hydrodimeric to hydromonomeric products, i.e. the product-selectivity, depends on substrate concentration, mass transfer coefficient and current density. Model calculations are in agreement with experimental results from the electroreduction of p-methylbenzaldehyde using a rotating cylinder cathode and explain a drastic effect of mass transport on the product-selectivity.