Localised corrosion attacks and oxide growth on copper in phosphate-buffered saline

Phosphate-buffered saline (PBS) is a buffer commonly used in antibacterial surface research. However, how copper surface varies in the buffer, in terms of corrosion attacks and oxide growth, is not yet fully recognised. In this study, PBS was applied as droplet on two types of copper surface: ground and electropolished. By scanning electron microscope (SEM), the similarities of their corrosion sites were compared, revealing the initiation of intergranular attack and orientation-dependent crystallographic etching. High resolution grazing incidence X-ray diffractometer (GIXRD), optical microscope (OM), Raman spectroscopy, and electron backscatter diffraction (EBSD) together provided detailed description of the epitaxial growth of cuprous oxide (Cu2O) on electropolished copper. The amount of copper ions released from two types of surface were determined by inductively coupled plasma mass spectrometry (ICP-MS). By introducing E. coli into PBS, the inhibition of Cu2O growth on electropolished coupon was observed. However, bacteria were found to hardly alter the corrosion mechanisms or the distribution of corrosion sites.