An electrochemical method to study scaling by calcium sulphate of a heat transfer surface

The main purpose of this investigation was to devise an electrochemistry-based method, using the assessment of the oxygen–reduction cathodic reaction, in order to evaluate the intensity of calcium sulphate scale formation on a heat transfer surface. For this purpose, an experimental device, permitting the simultaneous measurement of the surface temperature and the current intensity relative to electrochemical oxygen–reduction on the heat transfer surface during the fouling process, was built. From the chronoamperometric curves, it is possible to deduce the induction time. The results were confirmed by the simultaneous direct measurement of the surface temperature. This coupling of thermal and electrochemical measurement gave additional information regarding the growth and the porosity of the formed scale layer. By this chronoamperometric method, it was shown that the supersaturation coefficient of a saturated calcium sulphate solution must exceed a critical value ΩcΩc of the order of 4 to observe the crystallization of the gypsum layer. For the same saturation level, the salt concentration has a stronger effect than the temperature on the precipitation process.