Abstract: A description is given of antifreeze concentrates which comprise a) at least one water-miscible alcohol which lowers the freezing point; b) at least one corrosion inhibitor; and c) as reserve alkalinity donor, at least one mono- or polycyclic aromatic compound which has at least one hydroxyl group and a high buffer capacity in the pH range from about 6 to 10 and of coolant compositions which comprise said concentrates and are intended for the cooling circuits in internal combustion engines.

Abstract: Quaternized imidazoles I ##STR1## in which R.sup.1 and R.sup.3 independently of one another are saturated or unsaturated hydrocarbon radicals of 1-12 carbon atoms which can be substituted by oxygen-functional groups or interrupted by nonadjacent oxygens,R.sup.2, R.sup.4 and R.sup.5 independently of one another are hydrogen or saturated or unsaturated hydrocarbon radicals of 1-12 carbon atoms which can be substituted by oxygen-functional groups or interrupted by nonadjacent oxygens, it being possible for R.sup.4 and R.sup.5, together with the corresponding imidazole carbons, to form a five- or six-membered ring, andX.sup..crclbar. is an anion,are used as corrosion inhibitors in the corrosion protection of nonferrous metals, especially for car radiator protection.