Electrodeposition of CaCO3 on stainless steel 316 L substrate: influence of thermal-hydraulics and electrochemical parameters

Abstract

In this paper we study the effect of the hardness, the rotation speed, the temperature and the cathodic polarization on calcium carbonate scale deposit on rotating stainless steel electrode using electrochemical techniques. The scale deposit was investigated by X-Ray diffraction, scanning electron microscope, Infrared spectroscopy and electrochemical impedance spectroscopy (EIS). The electrochemical results show that the Oxygen Reduction Reaction (ORR), which is responsible of CaCO3 electrodeposition, takes place with 4 electrons at low rotation speed lower than 600 rpm and 2 electrons at high rotation speed upper to 1000 rpm. The recovery times of concentrations: 100, 300 and 600 mg/L are respectively 2.0 h 20 min, 1 h 20 min and 1 h. The morphology of the CaCO3 scale deposit shows that the crystals formed in the center of the electrode have small sizes compared to those of the periphery. Whatever the hydrodynamic or thermodynamic conditions, the Calcite form remains predominant. Other forms appear in particular conditions: at high temperature up to 50°C the aragonite form and at high cathodic polarization about -1.2 V/SCE the vaterite form.