A water-dilutable epoxy resin composition ABC of an epoxy resin AB and an emulsifier C, a process for its preparation, and a method of use thereof to make elastic coating films that impart good corrosion resistance even in thin layers. The epoxy resin AB featuring, in its polymer chain, moieties derived from aliphatic polyethers B1 having at least 4 carbon atoms in the alkylene group or from aliphatic polyesters B2 based on linear, branched or cyclic aliphatic polyhydric alcohols B21 and linear, branched or cyclic aliphatic polyvalent acids B22, where the average number of hydroxyl or acid groups in B21 or B22 is at least 1.9. The emulsifier C is a reaction product of an aliphatic polyol C1 and an epoxy resin C2.