Bulk and Surface Hydrogen Concentration Differences in NBS Hydrogen-In-Titanium Standards

The objective of this study was to evaluate the use of NBS hydrogen-in-titanium standards as reference standards for localized surface hydrogen analysis. A newly developed low energy spark probe was utilized to facilitate such analyses to a depth of a few microns from each specimen surface. It was found that the NBS samples had hydrogen concentration gradients from the surface into the bulk of the material. The results of the bulk hydrogen analysis in each instance was in excellent agreement with the NBS certified values. This implies that these specimens are primarily designed as reference standards for bulk analysis. Results of the present study are compared with lithium microprobe data and critical sources of error in such localized measurements are discussed.