Effect of calcium cation (Ca++) on the rate of deposition of ∝‐iron oxide on heated surfaces in boiling water

Abstract

The specific influence of calcium and sodium cations on the rate of deposition of a‐Fe2O3 (a main corrosion product in boilers and heat exchangers) has been experimentally studied. A deposition model based on the microlayer evaporation and dryout phenomena that occur in the nucleate boiling bubble is put forward for interpretation of the deposited layer. It has been found that the rate of deposition of Fe2O3 increases with the increase in valency of the soluble cations. With calcium, the deposition rate increases linearly with the increase in its ionic concentration, whereby the rate is increased by 5.9, 6.8 and 7.6 with 200, 400 and 600 ppm calcium respectively. Development of the deposition layer takes place in the valleys of the surface contour according to a micro‐layer evaporation mechanism. Successive deposition is performed at the periphery of the first deposit. Reduction in cation content in the crude solution and selecting smooth heated surfaces are recommended to reduce the ∝‐Fe2O3 deposition on heated surfaces in boiling water.

Citation

Rabah, M.A., Eldighidy, S.M. and Aboukhashaba, A.A. (1983), "Effect of calcium cation (Ca++) on the rate of deposition of ∝‐iron oxide on heated surfaces in boiling water", Anti-Corrosion Methods and Materials, Vol. 30 No. 4, pp. 7-11. https://doi.org/10.1108/eb007218