Disclosed are methods of using biodegradable heterocyclic compounds of relatively low toxicity as corrosion inhibitors. The present method is used to inhibit corrosion of a metal surface in contact with an aqueous system using compounds comprising a purine structure, and provides enhanced protection against corrosion of metals in aqueous systems. The method comprises the use of corrosion inhibitors that are generally resistant to halogen attack and provide good corrosion resistance in the presence of oxidizing halogen-based biocides. Formulations comprising purine-based compounds are also disclosed.