Because of the toxicity of hexavelant chromium ion, treatments of metallic surface with chromate compounds to retard corrosion are undesirable for safety control in industrial uses and protection of environment. In this study, we investigated several compounds such as inorganic, organic, and polymer materials in order to substitute the chromate conversion treatment on steel sheet. The corrosion property was investigated in a salt spray tester with 3.5 wt.% NaCl at 35℃. The results showed that the zirconium/silane/polymer triple coatings on the galvanized steel exhibited a significant retardation of corrosion. Although the multicoating system needs a complexed processing, we can confirm a possibility of development of a chromate-free chemical conversion treatment for galvanized steel sheet.

The purpose of this theses is to examine the influence of school forests on students' temperament. To collect data, 1,425 students (655 students in experimental group and 710 students in control group) were surveyed during fall semester of 2002. The results of this study indicated that forests in school have significant influence on students temperament. Especially elementary school students showed much stronger influence than middle and high school students.