The effect of electrochemical charging of hydrogen on the structure of a lean duplex stainless steel LDX 2101 (R) (EN 1.4162, UNS 532101) was examined by both Time-of-Flight secondary ion mass spectrometry and electron back-scatter diffraction. The goal is to correlate hydrogen concentration and induced structural changes. Chemical and structural characterizations were done for the same region at the sample's surface with sub-micron spatial resolution. Regions of interest were varying in size between 50 x 50 mu m and 100 x 100 mu m. The results show a phase transformation of austenite to mainly a defect-rich BCC and scarcely a HCP phase. The phase transformation occurred in deuterium rich regions in the austenite. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.