The investigation of the film structure and hydrogen embrittlement resistance of Zn-Ni-SiO₂ composite plating film and Ti-Cd plating film with excellent hydrogen embrittlement resistance demonstrated that the Zn-Ni-SiO₂ composite plating film plated from acidic chloride bath had equal hydrogen permeability to that of the Ti-Cd plating film. Furthermore, cross-sectional observation revealed the structure of Zn-Ni-SiO₂ composite plating film. This crack structure presumably supports the high hydrogen permeability and the porous structure of Ti-Cd plating film.

These findings suggest that the Zn-Ni-SiO₂ composite plating film from an acid chloride bath has high functionality and effectiveness for application to high-strength components. This paper introduces the structure and hydrogen embrittlement resistance properties of this composite coating.

For this study, a piping system was constructed to simulate the kitchen drainage system of a typical apartment building. Vinyl chloride pipe and hot-dip galvanized carbon steel were selected as piping materials. Several materials with antimicrobial coatings were used. For several months, a simulated wastewater solution was poured into the system. The pipe inner walls were sampled periodically to observe internal contamination and scale formation with several frequently used pipe materials. Amounts of biofilm formation were evaluated quantitatively using crystal violet to evaluate the degree of staining. The study results are discussed, particularly addressing the biofilm inhibition capabilities of epoxy composite coatings with silver-loaded zeolite dispersions.