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Passive Layer (passive + layer)

Distribution by Scientific Domains

Polymers and Materials Science	75%

Selected Abstracts

Corrosion Behavior of PM Processed Ti,Ca,P Bioceramic Composites in Hank's Balanced Salt Solution Using Potentiodynamic Studies

INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 2 2010
Malobika Karanjai
Ti,Ca,P bioceramic composites for load bearing implants developed by a new powder metallurgy processing technique were studied for their electrochemical corrosion properties. For determining corrosion behavior of such composites having in situ formed bioactive Ca,P phases, potentiodynamic and studies were conducted in simulated body fluid namely Hank's balanced salt solution. Potentiodynamic polarization tests showed no evidence of pitting corrosion. Corrosion potentials (,0.27 to ,0.53 V) and corrosion rates (0.17,4.46 mills per year) of Ti,Ca,P bioceramic composite samples were superior to earlier reported results for coated Ti implants due to the formation of passive layer of bone-like calcium phosphate on the sample surface. [source]

Testing procedure to obtain reliable potentiodynamic polarization curves on type 310S stainless steel in alkali carbonate melts

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 4 2006
S. Frangini
Abstract Potentiodynamic polarization measurements have been employed to evaluate the anodic behavior of a type 310S stainless steel in the eutectic Li/K molten carbonate. In general, the electrochemical tests yield useful information to predict the stability of the oxide films formed on the surface at the initial period of corrosion, although some precaution is required in the testing procedure as the reproducibility of results is seen to be adversely affected by the passage of large currents. Especially when the steel is in a passive state, erratic results are easily observed if the corrosion layer is being damaged by uncontrolled large currents. This is because the acid-base properties of the melt are susceptible to deep changes by applied currents in the milli-ampere range resulting in hysteresis phenomena in the polarization plot. Hysteresis is caused, on one hand, by acidic dissolution of the passive layer at high anodic currents and, on the other hand, by increased melt basicity due to oxide ion build-up at high cathodic currents. An optimized testing procedure is therefore suggested that minimizes these effects by imposing a 2 mA/cm2 threshold current during polarization measurements. Moreover, the conditions for the applicability of the linear polarization technique to estimate kinetic parameters have been discussed in relationship with the corrosion mechanisms analysed by impedance spectra. It is concluded that the presence of diffusional impedance terms and formation of surface resistive films in molten carbonates may result in not reliable polarization resistance values obtained with the linear polarization. [source]

Synergistic or additive corrosion inhibition of mild steel by a mixture of HEDP and metasilicate at pH 7 and 11

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 11 2004
D. Mohammedi
Abstract Electrochemical measurements (steady-state current-voltage curves and AC impedance) were coupled with mass-loss measurements, SEM examinations, and EDSX analyses to investigate the inhibition of corrosion of a carbon steel by a mixture of phosphonic acid HEDP (acid 1, hydroxyethylene, 1-1 diphosphonic) and sodium metasilicate pentahydrate Na2SiO3. 5H2O in an industrial hard water containing 3.10,3 M Ca2+ ions. At pH 7, HEDP and Ca2+ act in a synergistic manner, by formation of a HEDP and calcium containing layer. Addition of silicate at this pH value, allows to reach an efficiency of 94% due to an additive inhibition effect. At pH 11, metasilicate, HEDP, and Ca2+ ions reinforce the passive layer in a synergistic way. The mixture (1.7 · 10,5 M HEDP + 2.6 · 10 -3 M SiO2,3) in the Ca2+ containing electrolyte is shown to be able to inhibit efficaciously the corrosion of iron at room temperature, considering uniform corrosion at pH 7 or pitting corrosion at pH 11. [source]

Stationary solutions to an energy model for semiconductor devices where the equations are defined on different domains

MATHEMATISCHE NACHRICHTEN, Issue 12 2008
Annegret Glitzky
Abstract We discuss a stationary energy model from semiconductor modelling. We accept the more realistic assumption that the continuity equations for electrons and holes have to be considered only in a subdomain ,0 of the domain of definition , of the energy balance equation and of the Poisson equation. Here ,0 corresponds to the region of semiconducting material, , \ ,0 represents passive layers. Metals serving as contacts are modelled by Dirichlet boundary conditions. We prove a local existence and uniqueness result for the two-dimensional stationary energy model. For this purpose we derive a W1,p -regularity result for solutions of systems of elliptic equations with different regions of definition and use the Implicit Function Theorem. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]