Accuracy of the linear gradient approximation for diffusion-controlled growth of iron sulfide scales
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The growth of a defective scale is analyzed in terms of an idealized, singlelayer, moving-boundary problem with constant diffusivity. The form of the solution is chosen to emphasize the magnitude of the departure from a linear concentration gradient of the diffusing species in the growing scale. The departure is shown to be a function of the k p /D ratio (where kp is the parabolic rate constant, and D is the chemical diffusivity), and thus is directly related to the defect concentration. For iron sulfide under most conditions, and for other compound scales with defect concentrations less than about 10%, the linear gradient assumption is shown to be reasonable.
Key WordsDiffusion layer growth defects iron sulfide
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- 1.E. M. Fryt, W. W. Smeltzer, and J. S. Kirkaldy,J. Electrochem. Soc. 126 673 (1979).Google Scholar
- 2.E. M. Fryt, V. S. Bhide, W. W. Smeltzer, and J. S. Kirkaldy,J. Electrochem. Soc. 126 683 (1979).Google Scholar
- 3.M. Danielewski, S. Mrowec, and A. Stoklosa,Oxid Met. 17 77 (1982).Google Scholar
- 4.M. Danielewski, S. Mrowec, and A. Stoklosa,Solid State Ionics 1 287 (1980).Google Scholar
- 5.R. E. Pawel,J. Electrochem. Soc. 126 1111 (1979).Google Scholar
- 6.M. Danielewski, Bull. Acad. Pol. Sci. Ser. Sci. Chim.27 425 (1979).Google Scholar
- 7.J. P. Hirth and R. A. Rapp,Oxid. Met. 11 57 (1977).Google Scholar
- 8.For example, F. Booth,Trans. Faraday Soc. 44 796 (1948).Google Scholar
- 9.W. Yost, Chap 1 inDiffusion, (Academic Press, New York, 1960).Google Scholar
- 10.On the basis of X-ray measurements of R. Perthel,Ann. Physik 5 273 (1960); F. Gronvold and H. Haraldsen,Acta Chem. Scand. 6 1452 (1952).Google Scholar