Material corrosion rates

In all cases, realistic but conservative values of material corrosion rates were determined their values are summarized in Table XVII. The rates lie towards the high end of recorded data in order to err towards the pessimistic side of die spectrum. For modelling purposes, corrosion rates established in this way are designated BCRs and filler lifetimes. Where there is a paucity of data, e.g., in the case of the Pb-Bi eutectic, nuclear fuels, and certain filler materials, best use has been made of available information and judgement. It should be noted, however, that containment k factors, as described in Section 3.2 (Model Construction), effectively inhibit BCRs by restricting pathways through barrier materials. 

Removal of the corrosion product or oxide layer by excessive flow velocities leads to increased corrosion rates of the metallic material. Corrosion rates 2ire often dependent on fluid flow and the availability of appropriate species required to drive electrochemical reactions. Surface shear stress is a measure of the force applied by fluid flow to the corrosion product film. For seawater, this takes into account changes in seawater density and kinematic viscosity with temperature and salinity [33]. Accelerated corrosion of copper-based alloys under velocity conditions occurs when the shear surface stress exceeds the binding force of the corrosion product film. Alloying elements such as chromium improve the adherence of the corrosion product film on copper alloys in seawater based on measurements of the surface shear stress. The critical shear stress for C72200 (297 N/m, 6.2 Ibf/ft ) far exceeds the critical shear stresses of both C70600 (43 N/m, 0.9 Ibf/ft ) and C71500 (48 N/m, 1.0 Ibf/ft ) copper-nickel alloys [33]. 

Poterrtiostatic-poterrtiodynarrric simulations. In most of the available kinetic degradation models, the Butler-Volmer electrode poterrtial is the input variable, the output being a material corrosion rate arrd the cell crrrrent. Implicitly, it is assumed that the potential of the nanorrraterials is eqrral to the external/rrracroscopic applied potential. Agairt, the cell poterrtial evolution and the associated MEA durability cannot be predicted in this way. In fact, the... 

Delville, M., BoteUa, P., Jaszay, T., et al. (2002). Electrochemical study of corrosion in aqueous high pressure, high temperature media and measurements of materials corrosion rates applications to the hydrothermal treatments of organic wastes by SCWO, J. Supercrit. Fluid, 26, pp. 169-179. 

Material Corrosion rate, mm/year (mils/year) ... 

For many materials, corrosion rate has appeared to double for every 30 to 60°C increase in temperature. 

Salt content of the desalinated water depends on the SWRO plant recovery ratio and the quality of the membranes. The product may contain NaCl at a level below 100 mg/L and up to 1000 mg/L. That can be reduced by a second-stage membrane treatment of permeate as explained in the previous sections of this chapter. Using two- or three-stage SWRO systems to remove boron to lower levels will further reduce the sodium chloride salt content as weU. As the water quality is improved, however, the produced water would have very low mineral content (especially calcium hardness) and therefore would be more aggressive and may dissolve matter from the piping system and increase pipe material corrosion rate. 

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