The invention provides compositions comprising nitrogen containing chelating agents, which can be used to reduce the effects of zinc contamination on the vulcanization rates of polymercapto based cure systems for halogenated elastomers. Such chelating agents are effective at eliminating vulcanization rate inconsistencies due to zinc contamination, without inducing negative changes to the vulcanization reaction or the subsequent physical properties of the halogenated elastomer vulcanizate. The invention also provides methods of curing a halogenated elastomer using the inventive compositions, and for articles prepared from the same.