Active dissolution system

The following activities may be performed to qualify the installation of an automated dissolution system ... 

Freshly assembled cells are subjected to a series of formation cycles in order to activate the system. Cells are often sold in a charged but dry state, in which case the formation process is performed before the final cell assembly. Dry charged batteries can be stored indefinitely. Cells containing electrolyte should be stored in the completely discharged state since dissolution of silver oxide is then avoided. 

In order to determine the corrosion state of an active-passive system, the position of the corrosion potential relative to pp must be determined. According to Fig. 4, if Econ is below Ew, the material will undergo uniform dissolution under film-free conditions. If EC0II is above Epp but below Et, the material will be passive and will dissolve at its passive current density, which is often on the order of 0.01 mpy. Corrosion-resistant alloys are designed to operate under such conditions. For situations in which Ec0II is above Et, the material will dissolve transpas-sively, i.e., uniformly. 

Fig. 2D Schematic HE plots for a system undergoing corrosion and passivation. Active dissolution region A-B. Passive region C-D. Transpassive region where pitting occurs D-E.

Pickering and coworkers [31, 34, 35] have demonstrated both experimentally and computationally that for systems that meet the criteria of the IR theory, lA is predicted. The amount of potential drop increases as one moves into the crevice because of the current leaving the crevice. If the geometry, solution conductivity, and passive current density of the material in the environment conspire to create sufficient ohmic drop, then the potential of some portion of the material within the crevice falls to the primary passive potential. Under these circumstances, the passive film is not stable and active dissolution occurs. The potential difference between the applied potential and the primary passivation potential is referred to as IR. Deeper still into the crevice the ohmic drop leads to decreased dissolution as the overpotential for the anodic reaction decreases. Thus, ohmic drop is responsible for the initiation and stabihzation of crevice corrosion according to this model. 

As one may conclude from the results, water molecules activate dissolution of platinum atoms. The incorporation of Itydroxonium ions as well as positive charges in the system has no influence on the activation energy of platinum decompositioa... 

In homogeneous corrosion systems (active dissolution, passive state) where the same electrochemical reactions occur over the whole surface, the interrupter and ac technique can be successfully applied and the same value for the ohmic resistance is measured by both techniques. Problems arise in localized corrosion systems, where small active areas coexist with a large passive surface and the impedance of the active areas (pits) is short circuited by the surrounding passive surface. 

There are four 90 ml reservoirs in which to place predissolved amino acid solutions or amino acids as dry pow-ders for on-line dissolution. Depending on the selected coupling method, protected amino adds can be preactivalcd in the amino acid reservoirs followed by transfer to the reaction vessel for acylation. Alternatively, amino acids can be added directly to the reaction vessel for in situ activation. The system is supplied with seven solvcnt/rcagcnt reservoirs three 1 gallon and four 1 litre) to allow solutions for general... 

It is important to understand the mechanism of corrosion inhibition promoted by surfactant-based systems. The transition of the metal-solution interface from an active dissolution state to a passivation state is highly important in petroleum fields. Normally, surfactants are added to aqueous media to occupy the interface, hence reducing corrosion of the pipelines. It is known that increasing surfactant concentrations reduce interfacial tensions, as a result of enhanced aggregation and physical adsorption upon micelle formation at concentrations above the CMC. 

An example of the physical impregnation method is provided by U.S. Patent 4,302,565, which was discussed above. The dissolution of a magnesium compound and a titanium compound in a suitable solvent, usually an electron donor solvent such as tetrahydrofuran (THF), can lead to the formation of a new species (catalyst precursor) that provides a highly-active Ziegler system when activated. Removing the solvent at elevated temperatures in the presence of a support material such as silica will precipitate the precursor into the pores of the silica. In this method it is necessary that... 

The potential of the metal at which this occurs is called the equilibrium potential, If the system deviates from equilibrium, say through active dissolution, a new potential is established, which is related to the equilibrium potential by a term called the overpotential ... 

Current-potential curves for corroding systems (i) dissolution under active or passive conditions, (ii) cathodic reaction under mass transport control. A denotes the corrosion potential under active dissolution conditions and C under passive conditions. B denotes the potential following breakdown of the passive film where the dashed lines (iii) and (iv) are obtained by extrapolating the active dissolution lines. 

In the case of normal-temperature corrosion, nearly all metals/alloys are thermodynamically reactive in most natural enviromnents, for example in air. This is especially trae when the environment is moist, polluted or hot, and in water, especially when it is saline, acid or alkaline. There are various common corrosion behaviors of metals/alloys, the familiar patterns among which are active dissolution, passivation and local corrosion. This review focuses on three kinds of corrosion behavior and discusses the effect of nanocrystallization in a liquid system. NC materials have many useful applications and therefore better understanding of their stractural and chemical characteristics is of vital importance. 

Active dissolution of nanocrystalline materials in a liquid system... 

Extensive research has been carried out into NC materials because of the need for a basic understanding of the nature of nanostmctures and their potential technological apphcations. The preponderance of grain boundaries in NC materials increases the ratio of surface area as well as surface energy, which also increases the chemical activity in the materials. Therefore, if the materials exhibit active dissolution in a liquid system, the dissolution rate of the corresponding NC materials will be faster than traditional coarse ciystalline materials. 

Schematic polarization curve of a metal with active dissolution and passive range and a passivating redox system creating passivity (solid line) and maintaining...

Other redox systems may only maintain existing passivity. They compensate the small passive dissolution rates when passivity has been already achieved. These redox systems are too slow to overcome the active dissolution peak. Once the metal has been activated, the potential drops to a value in the active dissolution range with the related increased corrosion rate (Figure 1.48). 

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