(Invited) In-situ Evaluation of Brass Dezincification Corrosion Under Galvanostatic Polarization Combined with Video Observation

Abstract

Brass is widely used as the applications involving water supply pipes and pipe heat exchangers owing to its good mechanical properties. One of the limiting factors for use of brass is the dezincification corrosion, which may cause the water leakage accident. In the dezincification corrosion, the selective dissolution of zinctakes place on the brass surface, and the porous copper rich layer is formed on the brass surface1,2. To clarify the dezincification corrosion behavior of brass, we have newly developed a real-time cross-sectional surface observation system to examine the dezincification corrosion behavior of brass6. Our group developed a real-time surface observation system combined with video imaging to investigate the dissolution behavior of metals3-5. Comparing to the previous works3-5, the developed system in the present study allows for an in-situ monitoring of metal or alloy cross-section during electrochemical measurement because the video of metal or alloy cross-section can be taken by an optical microscope combined with a charge-coupled device camera. We applied the developed method for the investigation of brass dezincification corrosion, demonstrating that the inhomogeneous dissolution was observed in the depth direction under galvanostatic polarization. The average erosion depth could be estimated from the cross-sectional surface images at each measurement time. The results indicated that the depth erosion rate was different at initial and later stages, implying the preferential dissolution of zinc or the simultaneous dissolution of zinc and copper on the brass surface. Based on the video images and potential changes of brass during the measurement, the detailed dissolution behavior was discussed in the present study.References H.W. Pickering, C. Wagner, J. Electrochem. Soc., 7, 114 (1967). Y. Hoshi et al., J Solid State Electrochem, 19, 3551 (2015). Y. Hoshi et al., J. Electrochem. Soc., 164, C450 (2017). Y. Hoshi et al., Surf. Finish. Soc. Jpn., 69, 34 (2018). Y. Hoshi et al., J. Electrochem. Soc., 165, C243 (2018).Y. Hoshi et al., Mater. Trans., 64, 885 (2023).