1. AN IMPROVED LIQUID COATING COMPOSITON COMPRISING BETWEEN 20 AND 40%, BASED ON THE WEIGHT OF THE COMPOSITION, OF A SOLUBILIZED CROSSLINKABLE HYDROCARBON RUBBER CONTAINING AN AVERAGE OF AT LEAST ONE CARBON-CARBON DOUBLE BOND PER MOLECULE OF RUBBER, BETWEEN 1 AND 10%, BASED ON THE WEIGHT OF SAID RUBBER, OF A CROSSLINKING CATALYST, AN OXIDIZING AGENT FOR THE CATALYST AND BETWEEN 5 AND 15%, BASED ON THE WEIGHT OF SAID COATING COMPOSITION, OF ATRIORGANOTIN COMPOUND WHEREIN THE IMPROVEMENT RESIDES IN THE PRESENCE OF A LIQUID ISOBUTYLENE-ISOPRENE COPOLYMER RUBBER AND AT LEAST ONE LIQUID TRIORGANOTIN COMPOUND EXHIBITING THE GENERAL FORMULA R3SNX WHEREIN EACH R IS INDIVIDUALLY SELECTED FROM THE GROUP CONSISTING OF ALKYL RADICALS CONTAINING 3 AND 4 CARBON ATOMS AND PHENYL RADICALS, AND X REPRESENTS A PHENOXY RADICAL WHICH MAY CONTAIN AT LEAST ONE INERT SUBSTITUENT SELECTED FROM THE GROUP CONSISTING OF HALOGEN ATOMS AN D ARYL HYDROCARBON RADICALS, WITH THE PROVISO THAT THE CONCENTRATION OF THE SOLUBILIZED RUBBER IS BETWEEN 40 AND 80%, BASED ON THE COMBINED WEIGHT OF RUBBER AND SOLVENT, AND THE WEIGHT RATIO OF OXIDIZING AGENT TO CATALYST IS BETWEEN 2:1 AND5:1, RESPECTIVELY.