Dissolution Behaviors of Copper Metal in Alkaline H₂O₂-EDTA Solutions

Abstract

The dissolution behavior of Cu metal in hydrogen peroxide (H₂O₂)-ethylenediaminetetraacetic acid (EDTA) solution was studied through both electrochemical and chemical tests. In the electrochemical experiments, the open circuit potential (OCP) of Cu electrode at low H₂O₂concentration below 0.5wt% was determined by Cu anodic reaction and H₂O₂ cathodic reaction. On the other hand, the OCP in higher concentration above 2 w/t% of H₂O₂ approached to 70 mV vs. SCE, since the redox reaction of H₂O₂ was so dominant reaction that the Cu anodic reaction was masked. The anodic polarization curve of Cu around the OCP of 70 mV in the range between -200 and 200 mV in the solution without H₂O₂ showed the maximum Cu dissolution reaction front, while those of both carbon steel and Inconel 600 in the same potential range were situated in the passivation region. The anodic polarization behaviors of Cu in the H₂O₂ concentrations above 1 wt% were examined by a potentiostatic method along with a weight loss measurement. The anodic Cu dissolution current estimated from the weight loss measurement in the solution containing more than 1 wt% of H₂O₂ was higher than that predicted by the polarization curve of Cu in the H₂O₂-free solution. The dissolution reaction rate of Cu in the H₂O₂ solution linearly increased with H₂O₂ concentration. This result indicated that the dissolution reaction rate of Cu in the presence of H₂O₂ was enhanced by a reaction between Cu and H₂O₂, resulting in the shift of the polarization curves depending on H₂O₂ concentration. The experimental correlation equation based on the above results described well the overall dissolution reaction rate of Cu in H₂O₂ concentration ranges below 1 wt% and above 2 wt% in the EDTA solution.

KEYWORDS:

• chemical cleaning
• copper
• dissolution
• EDTA
• open circuit potential
• polarization
• concentration dependence
• hydrogen peroxide
• mixture