Abstract: A low toxicity, corrosion and scale inhibiting composition for use in recirculating aqueous systems, e.g. in heat exchangers, comprises from about 3-1,000 parts by weight of molybdate, from about 0.5-1,000 parts by weight of an organic cationic or non-ionic surfactant, from about 0.3-1,000 parts by weight of a water soluble polyphosphate and from about 0.05-500 parts by weight of an azole, for example tolyltriazole. The composition is water soluble or water dispersible, and is effective in very small amounts (3-3,500 ppm) for corrosion control of metals such as carbon steel, copper and aluminum exposed to circulating water.