Cu and Nb powders are co-added as intergranular modifiers to improve the corrosion resistance of Nd-Fe-B sintered magnets. For the magnet co-added with 0.2 wt.% Cu and 0.8 wt.% Nb, mass loss of accelerated corrosion test in 120 degrees C, 2 bar and 100% relative humid atmosphere for 96 h drops from 2.47 mg/cm(2) to 0.49 mg/cm(2) in comparison with the Cu/Nb free one. The corrosion potential E-corr in 3.5% NaCl aqueous solution increases from -1.115 V to -0.799 V, which indicates the better resistance against electrochemical corrosion. The improved corrosion resistance is ascribed to the enhanced stability of the intergranular phase by forming high electrode potential Cu-containing phase and reduced Nd-rich phase at triple junctions. Besides, the distribution of (Pr, Nd)-rich phases along the grain boundaries becomes more clear and continuous through Cu/Nb co-addition, maintaining fairly good magnetic properties of B-r = 13.6 kGs, H-cj = 11.4 kOe, (BH)(max) = 46.2 MGOe. Further investigation demonstrates that Nb is effective to refine the grains of hard magnetic Nd2Fe14B phase and Cu is beneficial for optimizing the distribution of the intergranular phases. (C) 2014 Elsevier B.V. All rights reserved.