Hydrolysis is an efficient method to generate in-situ H-2 from Mg-based waste. In order to produce hydrogen from these wastes by the hydrolysis reaction in seawater (i.e. 3.5 wt % NaCl), WE43 alloy was ball milled. WE43 is a magnesium-based alloy (i.e. W stands for Y and the first 4 indicates that the weight % of Y is 4; E stands for RE and the first 3 indicates that the weight % is 3). This alloy is known for its corrosion-resistant and flame-resistant behavior. The effect of the milling time, the nature of the additives (C and Ni) and the synergistic effects of both C and Ni were investigated. It has been established that a pre-milling for 3h is necessary to activate the alloy and to decrease sufficiently its particle size. On one hand, the presence of carbon provides the best hydrolysis performance compared to Ni (maximum theoretical yield reached in 12 min). On the other hand, the chronological order of the addition of both additives during ball milling affects the kinetics of the reaction. The mixture obtained by successive addition of Ni and C shows the best hydrolysis performances with a maximal yield reached in about 9 min. All the results are explained and discussed in terms of microstructural (XRD and SEM-EDS) and morphological (SEM) effects. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.