Heat-vulcanizable adhesives for the bonding of solids, the adhesive contains polybutadiene or a polybutadiene mixture and/or copolymers of butadiene with ethylenically unsaturated monomers and other vulcanizable components, and at least 0.5% by weight (based on the weight of vulcanizable components) of a metal salt as a hardening catalyst. The adhesive is particularly useful in vehicle assembly. The adhesive in less than 5 hours exposure to air forms a protective skin which imparts washer resistance to the adhesive.