Abstract: The invention described herein is a corrosion inhibitor concentrate, and a method for preparation thereof, which may be formulated free of nitrites, nitrates, amines, and phosphates. The inhibitor concentrate is a "single part" synergistic combination of inhibitors, stabilizers, and antifoam agents, useful for reinhibition of recycled antifreeze/coolant. The inhibitor concentrate is efficacious for corrosion inhibition in coolants across a broad range of glycol quality. The inhibitor concentrate comprises specific amounts of water, triazole, alkali metal hydroxide, borate, alkali metal silicate, silicate stabilizer, and anti-foaming agent.