In situ monitoring of deposition and dissolution of calcium carbonate by acoustic emission techniques associated to electrochemical measurements

Calcium carbonate (CaCO3) was electrochemically deposited from drinking water with different degrees of hardness (5, 19.6, 31.5, 69 and 150°F) on a copper surface. The roles of dissolved oxygen, rotating disc electrode (RDE) and copper surface state on the deposition of CaCO3 were investigated by electrochemical impedance spectroscopy (EIS). Acoustic emission (AE) techniques coupled to chronoamperometry were used to study the deposition of CaCO3 and its dissolution after adding a diluted hydrochloric acid (0.01M) in a water medium. CaCO3 deposition was characterized by an AE waveform with an amplitude lower than 30 dB and a power spectrum with a peak frequency around 230–260 kHz. Carbon dioxide evolution due to the dissolution of CaCO3 was characterized by an AE waveform with an amplitude in the range of 30–40 dB and a power spectrum with a peak frequency at 150 kHz. CaCO3 dissolution was characterized by a burst-type AE waveform with an amplitude higher than 40 dB and a power spectrum with a similar peak frequency as the deposition of calcium carbonate.