The invention relates to a process for preparing stable low-viscosity O/W rust-inhibiting emulsions, characterized in that a mixture having the following composition is employed for the formation of the emulsion:a) from 10 to 60% by weight of an oil component;b) from 1 to 10% by weight of an emulsifier component consisting of at least one addition product of from 2 to 20 moles of ethylene oxide to fatty alcohols having from 10 to 22 carbon atoms;c) from 1 to 10% by weight of a corrosion inhibitor consisting of at least one carboxylic acid having the general formula (I):R--COOH (I), wherein R represents a straight-chain or branched saturated or unsaturated alkyl moiety comprising from 6 to 22 carbon atoms or a moiety having the general formula (II): ##STR1## wherein R.sup.1 represents a saturated straight-chain or branched alkyl moiety comprising from 8 to 18 carbon atoms;d) from 0 to 10% by weight of co-emulsifier component consisting of at least one fatty alcohol comprising from 12 to 22 carbon atoms; ande) water as the balance.