Dissolution, state

K. Shinoda The Correlation between the Dissolution State of Nonionic Surfactant and the Type of Dispersion Stabilized with the Surfactant. J. Colloid Interface Sci. 24, 4 (1967). 

H. Kikuyama, M. Waki, M. Miyashita, T. Yabune, and N. Miki, A study of the dissolution state and the SiOa etching reaction for HE solutions of extremely low concentration, J. Electrochem. Soc. 141, 366, 1994. 

Shinoda, K. (1967) Correlation between dissolution state of non-ionic surfactant and type of dispersion stabilized with surfactant. /. Colloid Interface Sci., 24, 4. 

Figure 10 shows that when the current density applied is below 100 mAcm, a stationary dissolution state is reached, for which analysis showed that the reaction is Mo Mo (ni) + 3 e. 

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. 

N Funasaki, S Hada, K Suzuki. The dissolution state of a triglyceride molecule in water and its orientation state at the air-water interface. Chem Pharm Bull 24 731-735, 1976. 

Nakayama H, Kuwata H, Yamamoto N, Akagi Y, Matsui H (1989) Solubilities and dissolution states of a series of symmetrical tetraalkylammonium salts in water. Bull Chem Soc Jpn 62 985-992... 

The phenomenon of metal passivation, or sudden electrochemical potential-induced transition from an active dissolution state to a passive state, is responsible for the low corrosion rates observed in many metals and alloys. This condition has usually been attributed to the electrochemical formation of metal-oxide protection films or coverage of the surface by corrosion films. In either case, the metal becomes partially protected from the environment, and the corrosion current drops sharply. This condition is of enormous practical importance, as the integrity of metallic structures of great structural significance can be maintained by keeping their electrochemical potenticds at some predetermined ("passivation") value. 

Fig. rV-26. Steady-state diffusion model for film dissolution. (From Ref. 293.)... 

Anodic-stripping voltaimnetry (ASV) is used for the analysis of cations in solution, particularly to detemiine trace heavy metals. It involves pre-concentrating the metals at the electrode surface by reducmg the dissolved metal species in the sample to the zero oxidation state, where they tend to fomi amalgams with Hg. Subsequently, the potential is swept anodically resulting in the dissolution of tire metal species back into solution at their respective fomial potential values. The detemiination step often utilizes a square-wave scan (SWASV), since it increases the rapidity of tlie analysis, avoiding interference from oxygen in solution, and improves the sensitivity. This teclmique has been shown to enable the simultaneous detemiination of four to six trace metals at concentrations down to fractional parts per billion and has found widespread use in seawater analysis. 

The passive state of a metal can, under certain circumstances, be prone to localized instabilities. Most investigated is the case of localized dissolution events on oxide-passivated surfaces [51, 106, 107, 108, 109, 110, ill, 112, 113, 114, 115, 116, 117 and 118]. The essence of localized corrosion is that distinct anodic sites on the surface can be identified where the metal oxidation reaction (e.g. Fe —> Fe + 2e ) dominates, surrounded by a cathodic zone where the reduction reaction takes place (e.g. 2Fi + 2e —> Fi2). The result is the fonnation of an active pit in the metal, an example of which is illustrated in figure C2.8.6(a) and (b). 

C2.8.6(c). This increase occurs far below eitlier transpassive dissolution (oxide film dissolution due to tire fonnation of soluble higher oxidation states (e.g. Cr,0., ... 

Metals in higher oxidation states form halides which are essentially covalent, for example AICI3, SnCl, FeClj when these compounds dissolve in water they do so by a strongly exothermic process. Indeed it is perhaps incorrect to think of this only as a dissolution process, since it is more like a chemical reaction—but to differentiate for a particular substance is not easy, as we shall see. The steps involved in the case of aluminium chloride can be represented as... 

In an oversimplified way, it may be stated that acids of the volcanoes have reacted with the bases of the rocks the compositions of the ocean (which is at the fkst end pokit (pH = 8) of the titration of a strong acid with a carbonate) and the atmosphere (which with its 2 = 10 atm atm is nearly ki equdibrium with the ocean) reflect the proton balance of reaction 1. Oxidation and reduction are accompanied by proton release and proton consumption, respectively. In order to maintain charge balance, the production of electrons, e, must eventually be balanced by the production of. The redox potential of the steady-state system is given by the partial pressure of oxygen (0.2 atm). Furthermore, the dissolution of rocks and the precipitation of minerals are accompanied by consumption and release, respectively. 

Ores are mined and are then refined in an energy intensive process to produce pure metals, which in turn are combined to make alloys (see Metallurgy Mineral RECOVERY and processing). Corrosion occurs because of the tendency of these refined materials to return to a more thermodynamically stable state (1—4). The key reaction in corrosion is the oxidation or anodic dissolution of the metal to produce metal ions and electrons... 

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