Some of the archaeological bronze mirrors retain a smooth silver-gray luster but lack reflective functionality. A high-tin bronze mirror of Western Han Dynasty (202 BC-8 AD) which only showed basic polishing marks without any coating. The silver-gray luster area was the oxidized tin-rich α + δ eutectoid remaining after the loss of copper in α phase. Microscopic roughness causes light scattering, which is hard to normally reflect clear images. The polishing and copper loss could expose more tin area and form a dense oxide layer that enhances corrosion resistance by blocking active sites and isolating the bronze matrix. Even after thousands of years, mirror surface showed better chargetransfer resistance (Rct) and polarization resistance (Rp) than unpolished decorated surface, with max differences approximately 3 times and 5 times, respectively. Patina growth forms corrosion paths, destroying the resistance of the tin-rich surface, especially under green malachite.