Corrosion dissolution

FIGURE 1.5 Refractory surface wear dominated by chemical corrosive (dissolution). 

Metallization of PS by the wet chemical corrosive deposition is a subject of both scientific and applied interests [1-3]. The basic reaction of this process is substitution of silicon atoms by metal ones. Such reaction is an example of silicon corrosive dissolution under the oxidizing agent. The metals with a redox potential more negative than hydrogen may be only used as an oxidizer. 

SIMULATION OF CORROSIVE DISSOLUTION OF PT BINARY NANOCLUSTER IN ACID ENVIRONMENT OF POLYMER ELECTROLYTE MEMBRANE (PEM) FUEL CELLS... 

The aim of the present work is to develop a model of corrosive dissolution oiPt binary nanocluster Pt Me (Me Cr, Fe, Co, Ni, Ru) in working environment of low temperature fuel cells on the basis of quantum-chemical methods application and deduction of physico-chemical peculiarities ofPr (with different structure and elementary content) surface destruction under the influence of H O, Cl, OH, HjO. ... 

A model of corrosive dissolution of surfaces of platinum binary nanoclusters PtMe (Me is the transition metals Cr, Fe, Co, Ni, Ru) with shell structure in acid environment of low temperature fuel eells with the content of molecules and ions H O, CP, OH, based on ealeulations of adsorption of enviromnent eomponents with metal surface and activation barriers for dissolution of Pt atoms by means of quantum-ehemical methods PM6 and DFT. 

Chapter 8 is devoted to the simulation of corrosive dissolution of Pt binary nano-cluster in acid environment, of polymer electrolyte membrane fuel cells. It is well known that under the present catalytic electrode production for low temperature fuel cell, it is necessary to reduce their costs by the proposal of binary platinum nanoclusters PtX (where X are the transition metals Cr, Fe, Co, Ni, Ru), while such nanoparticles may possess high... 

XRR has been applied to the study of EEIs on several systems [201-205]. The technique was found to be sensitive not only to the formation of reaction layers but also to mass loss at the electrode surface due to processes of corrosion (dissolution) [201]. Of particular interest is the application of high energy synchrotron beams as sources, as their deep penetration capabilities enables the design of operando cells (Fig. 7.10a) [203], Therefore, uncertainty due to equilibration in the absence of an electrochemical potential is eliminated. The structural and chemical stability of EEIs during the lithium insertion/extraction processes have thus been evaluated (Fig. 7.10b) [201-204]. The dependence of these irreversible reactions on the crystal facet of the electrode material forming the EEI was established. It was found that electrolyte decomposition processes were coupled with the redox process occurring in the bulk of the electrode, which is a critical piece of information when designing materials that bypass such layer formation. 

Thus it can be seen that corrosion (dissolution of the metal) is an electrochemical process. Rusting does, however, require an additional oxidation step. If the final corrosion product can be formed as a strongly adherent, insoluble and impermeable layer on the metal surface, corrosion will decline, but if it is loose or permeable, the corrosion process will continue. In real life, the above processes are modified by the presence of other chemical species, even in trace amounts, and on steel the layer is commonly loose and permeable. In fact, corrosion can be inhibited by one of the following techniques ... 

It is well known that aluminum as such is fairly passive, because a very dense and uniform aluminum oxide AI2O3 layer is formed onto the metal to protect the metal from corrosion. Highly ductile light weight aluminum alloys that are passed through specific heat treatments can, however, make aluminum susceptible to corrosion. These materials may contain alloying elements such as magnesium and/or copper, which alter and complicate the corrosion behavior of aluminum. Typical forms of corrosion for the alloys are localized and pit corrosion. Due to the dense structure of the aluminum oxide layer, the corrosion rate of aluminum alloys is, however, substantially slower compared with corrosion/dissolution of CRS or HDG steel [15]. 

A model of the ORR in a single water-filled pore with charged walls of Pt will be presented. It affords the definition of an effectiveness factor, by which the performance of any nanoporous CL material could be evaluated. Furthermore, a remarkable conclusion is drawn in view of the coupling of ORR kinetics and metal corrosive dissolution. 

These results clearly show that the corrosive dissolution at E=Eq only reduces the fatigue resistance of the two-phase alloy when the a-phase is plastically deformed. To confirm this influence of the plastic deformation behavior of the a-phase, corrosion fatigue tests have been conducted at E=Eq on specimens aged at 400 °C for... 

Curie temperature Transition temperature of a material from ferromagnetic to paramagnetic. Galvanic corrosion Dissolution of metal driven by macroscopic differences in electrochemical potential, usually as a result of dissimilar metals in proximity. 

Melter-Created Glass Defects. Despite best efforts to generate a perfectly uniform glass melt, within any melter there are naturally occurring processes that oppose those efforts. These include refractory corrosion (dissolution), electrode corrosion, and preferential volatilization of some species from the melt surface. These produce localized and sometimes more global deviations from the desired glass composition. Localized composition deviations lead to inhomogeneities in the product, called cord and striae. 

The change of character of Cr+ from being protective to being soluble Cr at more noble potentials. The impurities segregates affect the flow of electrons and the rate of corrosion. Dissolution would depend on how conductive are the impurities at the grain boundaries. 

The effect of materials chemistry and microstructure of materials in SCC and the interrelationship between the two is highly complex. The composition of the alloy has a significant bearing on the properties of the passive films and phase distribution. For example, a high amount of carbon in steels tends to form chromium carbide which causes sensitization of steel and leads to intergranular corrosion. Similarly, impinity elements in steels segregates and affects the corrosion dissolution process. 

---