Pseudo-passivation

In certain concentrated acidic solutions, e.g. H2SO4, nickel, whilst not truly passive, may exhibit pseudo-passivity owing to crystallisation of a layer of nickel salt (in cone. H2SO4 probably /3-NiS04-6H20) on the surface". ... 

Krishnamurthy et al. (1988 b) found significant refinement of microstructure in rapidly solidified alloys, with the maximum refinement occurring near the quenched surface of the ribbons. Anodic polarization of the ribbon showed a pseudo-passivation effect which led to a significantly lower current density. Hehmann et al. (1989) compared the corrosion of rapidly solidified Mg-Al alloys containing 10-24% Al in aerated 0.001 M NaCl solution with that of chill-cast alloys of the same composition. Electrochemical characterization revealed a... 

Mg alloys incorporate rare earth (RE) elements [128] to improve (i) creep resistance, which is primarily achieved by RE-containing phases along grain boundaries [129,130], (ii) castability, (iii) age hardening [131], and corrosion resistance [132]. Chang et al. [132] reported that Mg-3Nd-0.2Zn-0.4Zr had a corrosion rate lower than AZ91D. Nordlien et al. [133] reported that RE elements improved passivation. Krishnamurthy et al. [134] suggested that pseudo-passivation in rapidly solidified Mg-Nd was due to Nd enrichment at the surface. 

The investigative mission is conducted in the context of an alliance whose spirit and goals are entirely collaborative. This does away with the tension induced by the pseudo-neutrality and passivity of the Freudian psychoanalyst. Also eliminated are such concepts as resistance and regression, because neither is either necessary or helpful. 

It should be mentioned that passive layers are not protective in all environments. In the presence of so-called aggressive anions, passive layers may break down locally, which leads to the formation of corrosion pits. They grow with a high local dissolution current density into the metal substrate with a serious damage of the metal within very short time. In this sense halides and some pseudo halides like SCN are effective. Chloride is of particular interest due to its presence in many environments. Pitting corrosion starts usually above a critical potential, the so-called pitting potential /i]>j. In the presence of inhibitors an upper limit, the inhibition potential Ej is observed for some metals. Both critical potentials define the potential range in which passivity may break down due to localized corrosion as indicated in Fig. 1. 

Pseudo triple-resonance experiments for passive selection of Y satellites... 

Fig. iL Pulse sequences for pseudo triple-resonance experiments with passive selection of satellites (a) z-filtered 2D-"X, H( "Y) INEPT. (b) -BIRD H,"X( "Y) HMQC. (c) H,"X( "Y) HMQC experiment with biselective excitation pulse (bis) biselective excitation may be achieved with DANTE or P-BIRD sequences, binomial pulses, or shaped pulses. (d) H, X( "Y) HEED-INEPT." ... 

Pseudo-homogeneous models can only be used for passive cases as shown in runs 1-3. 

In this paper we describe a model of a cup plater with a peripheral continuous contact and passive elements that shape the potential field. The model takes into account the ohmic drop in the electrolyte, the charge-transfer overpotential at the electrode surface, the ohmic drop within the seed layer, and the transient effect of the growing metal film as it plates up (treated as a series of pseudo-steady time steps). Comparison of experimental plated thickness profiles with thickness profile evolution predicted by the model is shown. Tool scale-up for 300 mm wafers was also simulated and compared with results from a dimensionless analysis. 

In most cases VOC degradation in iron reactors has been described by a pseudo first order rate law with respect to dissolved VOC concentration normalized to tile BET iron sm-face. Other kinetic expressions are used to consider reactive site saturation and increased iron surface passivation (e.g. Wust et al., 1999 Farrel et al., 2000) or more complex reaction pathways (Arnold and Roberts, 2000). The objective of this study is to evaluate three principal processes related to problems of temporal upscaling, i.e. lag time processes, the effect of flow velocity on degradation rates and the extent and effect of passivation reactions. 

The information provided by the equilibrium isotherms depicted in Figure 29.5 confirms the commercial selective carrier bis(2,4,4-trimethylpenthyl) phosphinic acid (Cyanex 272) as a suitable reagent to formulate the liquid membrane due to its capacity to selectively separate iron and zinc from chromium under the typical pH conditions of the passivation baths. Therefore, the typical composition of the pseudo emulsion employed in the EPT regeneration process contains Cyanex 272 and sulfuric acid as stripping agent, and the extraction and BEX of zinc and iron are described, respectively, by the following reversible chemical reactions ... 

Analysis of Passive Earth Pressure and Displacements of Retaining Walls Using Pseudo-Dynamic Approach... 

The seismic effects are generally considered as pseudo-static forces to be added to the other static forces. A detailed review ofthe literature regarding the computation of passive earth pressure using planar failure, composite failure mechanism and experimental investigations are presented in the following sections. In addition, the review of the literature for the computation of earthquake-induced displacements is also presented. 

Studies Pertaining to Pseudo-Static Passive Earth Pressures... 

Choudhuiy and Nimbalkar (2005) computed the seismie passive earth pressure distribution using pseudo-d5mamie approach. The total seismie passive earth pressure (P ) ean be defined as... 

---