Corrosion solubility data

Maximum Dissolved Corrosion Product, from Solubility Data (2 x 10 g of AI2O3 per titer at 1.5-liters/hr refreshment) 2.4 mgfcm2 0.14 mg/cm2... 

Thornton, E. W. Activity transport mechanisms in water cooled reactors. Report IAEA TECDOC-667 Coolant Technology of Water Cooled Reactors, Vol. 3 Activity Transport Mechanisms in Water Cooled Reactors., Vienna, 1992, p. 9—51 Walker, S. M., Thornton, E. W. Reanalysis of oxide solubility data. Proc. 5. BNES Conf Water Chemistry of Nuclear Reactor Systems, Bournemouth, UK, 1989, Vol. 1, p. 89—95 Walton, G. N., Hesford, E. The migration of activated corrosion products in high-pressure water loops. Proc. Conf Corrosion of Reactor Materials, Salzburg 1962, Vol. 2, p. 547-556... 

A fresh lead surface slowly oxidizes into a thin, protective lead oxide (PbO) that stops further oxidation of the metal. Lead gives satisfactory resistance to corrosion in rural, marine, and industrial environments. The corrosion rate data for lead is shown as 0.5-0.7 pm/y in industrial (New York, NY), 1.2-2.2 pm/y in marine (Kure Beach, NC), and 1.05-1.85 pm/y in rural (State College, PA) [6]. Lead corrosion products in such environments, in addition to lead oxide, are sulfate, chloride, and carbonate, with lead chloride being the most soluble of all four products (see Table 1). However, lead in outdoor exposures was found to produce sulfate (PbS04) and/or carbonate (PbC03), and indoor exposures lead carboxylates. The primary atmospheric agents responsible for degradation of lead are SO2, CO2, and carboxylic acid [7]. The corrosion rate of chemical lead in Key West, Florida, and La Jolla, California is 0.58 and 0.53 pm/y (0.023 and 0.021 mpy), respectively [2]. 

Well established corrosion resistance data are available for the most important steels. In aqueous solutions of 0.1 to 20% NaOH the corrosion rate of unalloyed and low-alloy steels at ambient temperature is less than 0.005 mm year". At higher concentrations - 20 to 50% NaOH - a value of 0.01 mm year" will not be exceeded. These steels show a passive behavior because of the formation of a protective layer. The protective layer of magnetite is built up according to Eq. (1-32) magnetite has the lowest solubility of all iron oxides in alkaline solutions. 

Unsworth (1989) in a recent review of the role of R elements in the development of Mg alloys has listed the corrosion rates (table 5) of various experimental and commercially developed alloys when immersed in saltwater solutions. Some alloys contained specific R elements while others contained R additions which were a mix of elements with atomic numbers from 57-71. All of the alloys had been heat treated by solution aimealing followed by age hardening. For comparative purposes, some corrosion rate data from other sources (Uhlig 1963) for pure Mg and commercially pure Mg (99.8%) (Braun 1979) are included. The solid solubility at room temperature of most R s in Mg is very small. Thus, at the levels of R shown, most of them would be present as Mg-R intermetallic phases. 

The Af-HjO diagrams present the equilibria at various pHs and potentials between the metal, metal ions and solid oxides and hydroxides for systems in which the only reactants are metal, water, and hydrogen and hydroxyl ions a situation that is extremely unlikely to prevail in real solutions that usually contain a variety of electrolytes and non-electrolytes. Thus a solution of pH 1 may be prepared from either hydrochloric, sulphuric, nitric or perchloric acids, and in each case a different anion will be introduced into the solution with the consequent possibility of the formation of species other than those predicted in the Af-HjO system. In general, anions that form soluble complexes will tend to extend the zones of corrosion, whereas anions that form insoluble compounds will tend to extend the zone of passivity. However, provided the relevant thermodynamic data are aveiil-able, the effect of these anions can be incorporated into the diagram, and diagrams of the type Af-HjO-A" are available in Cebelcor reports and in the published literature. 

Dissolved oxygen reduction process Corrosion processes governed by this cathode reaction might be expected to be wholly controlled by concentration polarisation because of the low solubility of oxygen, especially in concentrated salt solution. The effect of temperature increase is complex in that the diffusivity of oxygen molecules increases, but solubility decreases. Data are scarce for these effects but the net mass transport of oxygen should increase with temperature until a maximum is reached (estimated at about 80°C) when the concentration falls as the boiling point is approached. Thus the corrosion rate should attain a maximum at 80°C and then decrease with further increase in temperature. 

Chemical condensation This occurs when soluble corrosion products or atmospheric contaminants are present on the metal surface. When the humidity exceeds that in equilibrium with a saturated solution of the soluble species, a solution, initially saturated, is formed until equilibrium is established with the ambient humidity. The contaminants have already been detailed and of the corrosion products, obviously sulphates, chlorides and carbonates are most important in this context. However, in some cases there is a lack of reliable data on the vapour pressure exerted by saturated solutions of likely corrosion products. The useful data was summarised in Table 2.7. 

The factors influencing the corrosion of metals in soil are more numerous than those prevailing in air or water, and the electrochemical effects are more pronounced. Moreover, soils vary widely in their composition and behaviour even over very short distances. It is difficult therefore to obtain reliable data. It is evident, however, that zinc has considerable resistance to corrosion when buried, and the greatest attack is caused by soils which are acid or contain large amounts of soluble salts. 

Mechanistically, in approximately neutral solutions, solid state diffusion is dominant. At higher or lower pH values, iron becomes increasingly soluble and the corrosion rate increases with the kinetics approaching linearity, ultimately being limited by the rate of diffusion of iron species through the pores in the oxide layer. In more concentrated solutions, e.g. pH values of less than 3 or greater than 12 (relative to 25°C) the oxide becomes detached from the metal and therefore unprotective . It may be noted that similar Arrhenius factors have been found at 75 C to those given by extrapolation of Potter and Mann s data from 300°C. 

What has long been sought and badly needed is a soluble weighting agent less corrosive than, and equally non-damaging as, the popular calcium and zinc halides. Preliminary laboratory and field data indicate TKPP may be the solution. 

All but one of the reactions in Figure 4 lead to the formation of the soluble TiO + ion this seems consistent with the observed changes in the visible absorption spectrum of the solid electrode. It may also be that other titanium species are formed in solution, such as peroxytitanium complexes like H Ti05 We have no direct evidence as to the identity of the solution species at this time, and have limited the candidate corrosion reactions shown in Figure 4 to those for which thermodynamic data are readily available. Nonetheless, the fact that titanium is observed in the electrolyte only upon extensive photocorrosion (and then in smaller amounts than strontium) suggests that the initial photocorrosion process involves the loss of strontium from the SrTi03, with the formation of Sr(0Ac)2 or SrSO. ... 

Fig. 2 distinguishes the domains of immunity, corrosion and passivity. At low pH corrosion is postulated due to an increased solubility of Cu oxides, whereas at high pH protective oxides should form due to their insolubility. These predictions are confirmed by the electrochemical investigations. The potentials of oxide formation as taken from potentiodynamic polarization curves [10] fit well to the predictions of the thermodynamic data if one takes the average value of the corresponding anodic and cathodic peaks, which show a certain hysteresis or irreversibility due to kinetic effects. There are also other metals that obey the predictions of potential-pH diagrams like e.g. Ag, Al, Zn. 

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