The use of electrochemical noise measurements to detect bad copper electrorefining conditions

Additives like thiourea, gelatin and chloride are used during copper electrorefining to promote a smooth deposit. However, additives can also facilitate nodule formation when their ratios and/or concentrations are inadequate. A preliminary investigation was conducted to determine if electrochemical noise (EN) measurements could be used to monitor and detect inefficient copper electrorefining conditions due to improper ratios and/or concentrations of additives. EN measurements were carried out in the laboratory under simulated industrial conditions. Galvanostatic experiments were conducted using a synthetic electrolyte containing different concentrations of additives. A 316L SS cathode and industrial copper anodes were used. The effects of three different data acquisition frequencies were also investigated. EN signals obtained as potential time record series were studied using statistical analyses and frequency domain transforms. The different calculated parameters gave similar results for all conditions studied except when additives present in the electrolyte led to nodule formation. Results also showed that the data acquisition frequency must be at least 10 Hz to detect improper ratios and/or concentrations of additives.