A combined bulk chemistry/electrochemical approach to study the precipitation, deposition and inhibition of CaCO₃

Scale deposits such as CaCO₃, BaSO₄ and CaSO₄, are a serious problem encountered in many industrial processes which involve precipitation of minerals onto the walls of water handling equipment from process water. The consequences of scaling are numerous; namely lowered heat transfer efficiency, increased pumping costs, total or partial blocking the water flow and the requirement for frequent system cleaning. An electrochemically based technique using assessment of the oxygen-reduction cathodic reaction has been devised, which allows the extent of scaling on a solid surface to be determined. This technique is based on the correlation between the diffusional characteristics of oxygen at a surface and the changes in the rate of oxygen reduction once nucleation and growth of CaCO₃ occurs. Use of this technique in conjunction with bulk chemistry measurements has enabled the precipitation and deposition kinetics to be compared and contrasted in the absence and presence of a commercial scale-control inhibitor. In addition, the potential for this technique to study thermally driven scale is demonstrated.