To visually detect gas simply by providing treatment films different in gas barrier properties on a metal piece or film easily discolored by gas.
Treatment films 2 different in gas barrier properties are provided on a metal substrate 1 comprising a metal piece or film easily decolored by gas and silver, copper or iron is used as the metal substrate 1 and appropriately selected according to the kind of gas to be detected. For example, when the gas to be detected is hydrogen sulfide and chlorine gas, silver and copper are pref. When the metal substrate 1 comprises the metal film, as a method for forming a film on a substrate 3, a vacuum vapor deposition method, an ion plating method, a sputtering method or the like is used. Each of the treatment films comprises a coating film of a paint, a dry film formed by a vapor deposition or CVD method or the like and has transparency permitting the recognition of the surface change of the metal substrate 1. By this constitution, decoloration can be easily observed visually and, if there is decoloration, it can be immediately recognized.
NOGUCHI SHINJI
WATANABE KATSUMI
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