Quinolinium sulfonates of the formula I ##STR1## wherein R.sup.1 is C.sub.1 -C.sub.8 -alkyl, C.sub.1 -C.sub.4 -alkyl substituted by halogen, hydroxyl or C.sub.1 -C.sub.4 -alkoxy, or it is C.sub.2 -C.sub.8 -alkenyl, C.sub.7 -C.sub.9 -phenylalkyl or C.sub.5 -C.sub.8 -cycloalkyl, R.sup.2, R.sup.3, R.sup.4 and R.sup.5 independently of one another are each hydrogen, C.sub.1 -C.sub.4 -alkyl, halogen, --CN, --COO(C.sub.1 -C.sub.4 -alkyl), --CHO, hydroxyl, C.sub.1 -C.sub.4 -alkoxy, an acyloxy group R.sup.7 COO--, a group R.sup.8 --CH.dbd.CH--, C.sub.7 -C.sub.9 -phenylalkyl or phenyl, R.sup.6 is C.sub.1 -C.sub.12 -alkyl, C.sub.6 -C.sub.10 -aryl which is unsubstituted or mono- or polysubstituted by C.sub.1 -C.sub.12 -alkyl, C.sub.1 -C.sub.4 -alkoxy, halogen or a group R.sup.7 CONH--, or it is fluorine, NH.sub.2 or CF.sub.3, and R.sup.7 and R.sup.8 independently of one another are each C.sub.1 -C.sub.4 -alkyl or phenyl, are suitable as latent curing catalysts for acid-curable stoving lacquers. There is formed by irradiation with UV light the actual acid catalyst, which renders possible curing at relatively low stoving temperatures.