Abstract: Two-part, elastomeric sealant coatings curable at ambient temperature. The sealant contains a radical polymerizable component, an oxidizing agent and a reducing agent, and optionally an epoxy component, polar wax, and/or rheology modifier. The radical-polymerizable component contains 25 to 45 weight percent of alkacrylate monomer and unsaturated phosphorous monomer and 55 to 75 weight percent of an ethylenic unsaturated liquid elastomer polymer having a number average MW of from 3,000 to 9,500 and a backbone Tg less than ?30° C. The elastomer polymer makes up 32 to 55 weight percent of the sealant and epoxy component makes up 2 to 15 weight percent. The elastomeric sealant coatings provide corrosion protection over the seams and maintain a crack-free surface over a broad temperature range. The sealant coatings are useful for applying over seams of joined metal parts, especially weld seams in the manufacture of automotive unit bodies, doors, floors, hoods, trunks, and trunk lids.