Fine particle bombarding（FPB）is typically used to modify metal surfaces by bombardment with fine particles at high speed. After bombardment with particles ranging in diameter from several to tens of micrometers, fine microscale concavities and convexities are formed on a surface. We have reported that SUS304 stainless steel with such a microscale rough surface formed by FPB shows antibacterial activity. However, SUS304 includes some metal ions such as Co and Ni, which are known as antibacterial metals. To demonstrate that microscale roughness only expresses the antibacterial property, we coated diamond-like carbon（DLC）onto the FPB treated surface of SUS304 substrate, and used it for antibacterial property tests against Escherichia coli and Staphylococcus aureus. Consequently, we also confirmed that the DLC-coated FPB surface has antibacterial performance. This finding indicates that the antibacterial performance is not dependent on the material properties, but rather on the surface roughness.
This study was conducted to improve four characteristics as objectives:（1） high current efficiency, （2） high surface brightness, and （3） high hardness of chromium-carbon （Cr-C） alloy layers during electrochemical deposition from Cr（III） ions, and （4） reproducibility of the Cr-C layer formation during repeated plating with a Cr-C electroplating bath. A malonic-acid-containing sulfuric acid bath （sulfuric acid bath II） was prepared by adding an arrangement to a conventional sulfuric acid bath （sulfuric acid bath I）. The malonic-acid-containing sulfuric acid bath II achieves the four objectives. Optimizing the bath composition and the electrochemical deposition conditions of the sulfuric acid bath II containing malonic acid was accomplished with a 0.2 M added malonic acid concentration, a 1.5 pH bath, and 33.4 A dm－2 plating current density. The current efficiency under these optimized conditions was 55.9%. Also, the C co-deposition percentage was 39.7%. Using a plating bath with a sulfuric acid bath II containing 0.2 M malonic acid, testing for the Cr-C layer reproducibility was performed repeatedly when plating: both the current efficiency and the C co-deposition percentage continued to be greater than 55% and 39%, respectively. However, the surface uniformity of the Cr-C layer tended to decrease after the fifth plating. Comparison of the surface brightness with that achieved using conventional baths demonstrated that the 0.2 M malonic-acid-containing sulfuric acid bath II was able to maintain high brightness.