Electrochemical treatments for selective growth of different calcium carbonate allotropic forms on carbon steel.

Different allogropic forms of calcium carbonate scales (calcite and aragonite) were electrochemically deposited on carbon steel surfaces, using different electrochemical techniques: cyclic voltammetry or potentiostatic pulses. To simulate conditions of Mexican refinery cooling systems, this study was performed in the presence of known concentrations of other salts at pH 7.8 and 40 degrees C with low and high calcium carbonate concentrations. Reduction reactions for dissolved oxygen and water occurring in such systems modified the pH at the substrate-solution interface to promote scaling of the calcium carbonate present. A systematic scanning electron microscopy and X-ray diffraction analysis of the carbon steel surface showed that the formation of calcite and aragonite depended on the initial state of substrate surface (clean or damaged) and on the concentration of calcium carbonate present in the system.