Thin p-GaInP2 films were tested 24 h in pH1 NH4NO3 solution at AM 1.5 G, and compared to that tested in 3 M H2SO4. Optical, SEM and EDX investigations confirmed that the surface of the tested sample in pH1 NH4NO3 was kept almost as that of an as-received one, while the sample tested in 3M H2SO4 experienced extensive corrosion via selective dissolution of Ga. ICP analysis confirmed the very low dissolution of p-GaInP2 in pH1 NH4NO3 solution, compared to that in 3 M H2SO4. The GaInP2 sample tested in pH1 NH4NO3 solution had an XPS depth profile almost identical to that of an as-grown sample, we speculate that absorbed NH3 on the semiconductor surface could be responsible for the observed corrosion inhibition. Thus, the p-GaInP2 should last much longer when working in pH1 NH4NO3 solution, due to this inhibiting effect. This result shows promise toward meeting US DOE's 2013 goal of 8% STH efficiency for 1000 h duration. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.