A Simple System for Measuring Permeation of Hydrogen Through Stainless Steel

A simple laboratory experiment was constructed to demonstrate in a classroom setting hydrogen permeation under conditions typical of some nuclear applications. The goal was to allow students to find both solubility and diffusivity parameters for hydrogen moving through commercial stainless steel tubing. The purpose of the present work is to compare test results from this laboratory experiment with results from others to validate the experiment. Hydrogen mixed with argon was admitted to a heated test chamber containing a coiled Type 316 stainless steel tube. Pure argon sweep gas was passed through the tube to a process-gas mass spectrometer where composition transients of pertinent gas species were recorded. Fits of a theoretical transient model to the experimental data gave values of both diffusivity and solubility of hydrogen in the stainless steel tube. Tests were conducted at hydrogen partial pressures ranging from 1.7 to 83 kPa and tube temperatures from 636 to 770 K. The form of the permeation transient data was fit well by a classical theoretical model. Observed values of diffusivity and solubility of hydrogen in the stainless steel from these transients were similar to literature values with some notable differences. Evidence of permeation delay due to interference by the diluting Ar was observed. Limitations of the experimental system are discussed.