Papers by Keyword: Polarisation Resistance

Abstract: This research assesses the anticorrosive activity of Musa Paradisiaca (plantain peel extract) on AA6063 aluminum alloy when immersed in a 1M HCl solution. The plantain extract was tested in concentrations of 0.2g, 0.4g, 0.6g, and 0.8g and is considered a natural green corrosion inhibitor. The corrosion studies on AA6063 were carried out by the techniques of potentiodynamic polarization, optical microscopy, SEM/EDS, and XRD analysis. Also, tests were done in the range of 30°C to investigate the inhibition efficiency. It was observed from results that the plantain extract acts as a mixed-type inhibitor and it helps in reducing the corrosion rate by depositing a protective coating on the surface of the alloy. It was found from the Tafel plots that as the concentration of extract was increased, there was a decrease in corrosion current density (j_corr) and an increase in Polarisation Resistance (Rp). The adsorption mechanism agreed with the Langmuir isotherm suggesting that only monolayer adsorption took place. Analysis of the protective film by SEM/EDS and XRD revealed the presence of Fe₂O₃, CaO, Mg, SiO₂, and Zn components. Maximum inhibition efficiency of 82% was recorded at the extract concentration of 0.8g. The study highlights the potential of plantain extract to serve as a viable green inhibitor for aluminium in acidic medium.

Abstract: Development of a solid oxide fuel cell anode by impregnating catalytic Ni and Ni-CeO₂ nano-particles on 8YSZ fiber structure was carried out in this work. The nano-scale 8YSZ fibers were successfully fabricated by the electrospinning process and were well matched with the 8YSZ electrolyte. The experimental results demonstrated that the Ni/8YSZ anode with nano-8YSZ fibers, which impregnated with 3M nickel nitrate, decreases the polarization resistance and increases the exchange current density. However, the lowest polarization resistance and the highest exchange current density are observed in Ni/8YSZ fibers anode by adding nano-ceria particle from 5 wt.% to 10 wt.%. It is attributed to that the grain growth of Ni particle has been constrained by modifying appropriate amount of ceria particle to reduce the obstruction of diffusion path of fuel gas and to enhance the amount of triple phase boundary (TPB). On the other hand, 8YSZ nano-fibers provide a stabilized porous structure of the anode. Accordingly, nano-CeO₂ particle provides storing and releasing of oxygen ion to improve the catalytic performance of nano-Ni modified 8YSZ fiber anode

Abstract: In this paper, Sm_0.5-xGd_xSr_0.5CoO_3-δ (SGSC, x=0 and 0.2) powders were prepared using the solid-state reaction method. Their structure was identified by XRD. All powders formed the perovskite phase when calcined at 1100°C for 5 h. Sm_0.3Gd_0.2Sr_0.5CoO_3-δ/Gd_0.1Ce_0.9O_1.95 slurries were screen printed onto both surfaces of Gd_0.1Ce_0.9O_1.95 electrolyte and fired at different temperatures to fabricate the composite cathodes. The electrochemical property of the composite cathodes was characterized by the alternative current impedance spectroscopy. The impedance resistance of the composite cathodes increased with the increase of sintering temperature. For instance, the impedance resistance of the composite cathode fired at 1000 °C was 0.0875 Ω·cm² at 700 °C, while it was 0.175 Ω·cm² when fired at 1100 °C.

Abstract: A creep resistant Mg alloy MRI 230D was subjected to laser surface treatment using Nd:YAG laser equipped with a fiber optics beam delivery system in argon atmosphere. The laser surface treatment produced a fine dendritic microstructure and this treatment was beneficial for the corrosion and wear resistance of the alloy. Long-term linear polarisation resistance and Electrochemical Impedance Spectroscopy measurements confirmed that the polarisation resistance values of laser treated material were twice as high as that for the untreated material. This improved behaviour was due to the finer and more homogenous microstructure of the laser treated surface. The laser treatment also increased surface hardness two times and reduced the wear rate by 25% due to grain refinement and solid solution strengthening.

Abstract: Ti and Ti based alloys are characterised by a continuous electrochemical monitoring and a rapid straining electrode technique in simulated body fluid environment. Materials examined are Ti, Ti-6Al-7Nb, Ti-6Al-4V and Ti-29Nb-13Ta-4.6Zr. Sterilized specimens were immersed in Hanks solution or Eagle’s minimum essential medium (MEM) solution. Electrode potential and polarization resistance were simultaneously and continuously measured up to 7 days. For all the specimens examined, the corrosion potential reached to a steady state in 2 days for both solutions. On the other hand, corrosion resistance increased monotonously for the period examined. Tensile specimens were rapidly elongated under potentio-static polarization to evaluate the transient current after exposure of newly-created surface. The anodic current appeared during both elastic and plastic deformation. For Ti alloys, anodic current started to increase gradually during elastic deformation, then increased more rapidly to reveal a maximum when straining was stopped, then decreased. Pure Ti, on the other hand, revealed the transient current after plastic deformation, but does not show any current increase during elastic deformation. The larger dissolution for a straining was observed as the following order; Ti, Ti-29Nb-13Ta-4.6Zr, Ti-6Al-7Nb, then Ti-6Al-4V.