Reduction in Hydrogen Permeation through Diaphragm Used in Differential Pressure and Pressure Transmitters

Deuterium permeabilities through stainless steel diaphragms were measured. The diaphragms were oxidized 316L (100 μm), Au-plated 316L (Au (13 μm) /316L (100 μm) /Au (13 μm), Au (1 μm) /316L (100 μm)), and Al-laminated 316L (316L (50 μm) /Al (10 μm) /316L (50 μm)). A hydrogen permeation measurement system composed of vacuum chambers, a mass analyzer, and vacuum pumps was used. Hydrogen permeabilities through the diaphragms were found to be dominated by diffusion. Deuterium permeability through oxidized 316L decreased to 1/4 when the Cr content of the surface increased. However, the oxidized 316L was not an effective hydrogen penetration barrier. The deuterium permeabilities through Au-plated and Al-laminated 316L were 1/50-1/100 of that for 316L. It was found that the hydrogen permeability through Au-plated and Al-laminated 316L could be calculated from the permeability of Au and Al, because the permeability in the stainless steel is greater than those in Au and Al.