To form a glass coating layer of uniform thickness on the whole part of the inner wall of a hole in a metal substrate, by elecro-depositing the glass coating layer on the metal substrate surface, in electro-deposition liquid wherein nonionic surface active agent is added.
Dispersing medium is formed by adding nonionic surface active agent to mixture formed by adding water to 2-propanol. A metal substrate 11 is dipped in electro-deposition liquid formed by dispersing glass powder in the dispersing medium. By electro-depositing the glass powder on the metal substrate 11, a glass coating layer 12 is formed, and a porcelain substrate 10 is obtained. When the glass powder is electro-deposited on the metal substrate 11, polyoxyethylene groups in the nonionic surface active agent make crown ether arrangement, so that Ba2+ ions of glass component which are eluted by water content in the electro-deposition liquid are stabilized in 2-propanol. The Ba2+ ions are adsorbed on the glass surface by -OH groups or ester groups of the nonionic surface active agent, and the throwing power of glass powder to the metal substrate 11 is improved.
NAKAMURA MASAHIKO
UCHIDA KOJI
SHINOHARA YOSHINORI
