Thus, the invention relates to compounds of the formula I ##STR1## where R is aromatic, preferably phenylene, R.sub.1 and R.sub.2 denote C.sub.1 -C.sub.4 -alkyl, preferably C.sub.1 -C.sub.2 -alkyl, R.sub.3 denotes methyl or ethyl, x and z together denote a number from 2 to 360, preferably from 2 to 140, y denotes a number from 15 to 70, preferably 25 to 60, n denotes a number from 1 to 10 and A.sup.- denotes an anion, preferably chloride or bromide, a process for their preparation and their use as demulsifiers for demulsifying crude oil emulsions and as corrosion inhibitors in equipment for lifting and processing natural gas and crude oil.