Abstract: Alkane alkanolamines of the formulaRNHR.sup.1 OHwhereinR is hydrogen or normal C.sub.1-6 alkyl; and R.sup.1 is a normal or branched chain C.sub.2-4 alkyl or hydroxymethyl C.sub.2-4 alkylare effective to potentiate the activity of and prolong the useful life of antimicrobial agents in controlling the growth of microorganisms in industrial water based fluids. A specific example of the alkanolamines of this invention is n-hexyl ethanolamine.