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Hydrogen Permeation
Hydrogen Permeation is the penetration of hydrogen ions through the thin metal isolation diaphragms of a pressure transmitter or seal system. Over time, this penetration will cause errors in measurement. By picking the right isolation diaphragm material, this can reduce the rate of permeation. Historically, stainless steel has been the material of choice for general permeation protection. Although nickel-based materials like Hastelloy C and Monel offer greater corrosion protection than Stainless Steel, they are avoided due to their loose lattice structure. So for critical applications, gold plated SS diaphragms yield the best resistance to permeation. The gold plating adds a very thin layer of gold, which has a very tight lattice structure, prevents the penetration of hydrogen ions through the thin metal of the diaphragm.
Yokogawa offers several gold plating solutions, refer to the Application Note Hydrogen Permeation.
KB-2020-1002