For SUS 304/316/316L stainless steel materials, the typical Cr/Fe ratio is about 0.4. Since the Fe molecules are more active, they are more prone to cause a chemical reaction with external substances and corrode stinless steel; the chemical properties of Cr or Cr network element are more stable than the Fe compunds and are more resistant to corrosive solutions. After chemical polishing, the surface elements Cr/Fe ratio reaches 1.0 or even higher. The higher content of Cr on the surface layer, the corrosion resistance characteristics improves.