Tritium Autoradiography for Pure Iron

In order to locate hydrogen trapped in the microstructure of stainless alloys and/or steels, tritium autoradiographical studies have been carried out. We improved the techniques for autoradiography with the use of a corrosion inhibitor, NaNO2, during photographic processing, and obtained clear autoradiographs of tritium on iron. The techniques lead to the following conclusions: (1) The distinct autoradiographs for iron can be obtained by inhibiting the corrosion of the specimens by using a photographic processing solution containing sodium nitrite. (2) The resolution of the autoradiograph is higher than that obtained by the previous techniques, and the processing is simpler, because colloidon film is not used. (3) The grain boundaries and inclusions in cold worked and annealed iron act as trapping sites for hydrogen. (4) By using the techniques improved in this study, TEM and SEM as well as optical microscopy can be used to identify the trapping sites of tritium in iron in connection with its microstructure