STUDY ON THE ORIGIN OF SURFACE REDDENING OF 65-35-BRASS DURING THE STRIP PRODUCTION PROCESS

The surfaces of 65/35 brasses with normal and reddish color have been studied by XPS, EPMA and X-ray diffraction. Both are covered by thin surface films (2-3 nm thick) and reveal normal zinc contents at a depth of more than 10 mu m. However, the surface region of less than 1 mu m is dezincified. The dezincification is most serious in the surface within a depth of 10 nm under the surface film, particularly in the reddened sample. The skin depth of light with a wavelength of 1 mu m is about 4 nm for pure metallic copper and the thickness of the surface film is too small to cause the coloration. Reddening is due to the enrichment of copper at the underlying alloy surface by dezincification.