Hydrogen (H-1) trapped at intermetallic particles (IPs) in an aluminum alloy, 6061-T6, was visualized with secondary ion mass spectrometry (SIMS) by precisely excluding the false signal which is caused by background hydrogen (H-BG). The interference of the H-BG was avoided by a unique continuous pre-sputtering (pre-digging) by a primary ion beam of SIMS into a sample in combination with silicon sputtering prior to the SIMS measurement of the sample and we succeeded in visualizing the exact signal of H-1 trapped by IPs at subsurface layer of the sample charged in high-pressure hydrogen gas. The thermal desorption analysis clarified that the desorption energy (E-d) of the IPs was 200 kJ/mol or higher, which was extremely higher than Ed for lattice interstice, dislocations, and vacancies. High density hydrogen was concentratedly trapped at IPs in the subsurface layer in contact with the hydrogen gas. This nature causes an extremely low effective hydrogen diffusivity of 6061-T6 of the order of 10(-14) m(2)/s even at 200 degrees C and may eventually give a high HE resistance to 6061-T6. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.