A two-part adhesive formulation is provided that has an adhesive part A and an activator part B. The part A includes a monomer amount of a methacrylate ester monomer, a crosslinker amount of a polyfunctional monomer, an anti-oxidant, a free-radical polymerization inhibitor, and an adhesion promoter system to improve cured adhesive strength to a substrate, an impact modifier and a toughening agent and a free-radical polymerization initiator. The part B includes an impact modifier, butyl rubber, methacrylate ester monomer, and a free-radical polymerization accelerator yet varies in the weight ratio used relative to part A. Each of the part A and the part B have separate storage stability of at least 300 days at 23° C. A process of applying an adhesive to a substrate is provided that includes combining together parts A and B to form an adhesive mixture and applying the mixture to the substrate and allowed to cure.