Heat transfer fluid concentrates include: a freezing point depressant, water, or a combination thereof; an organophosphate; a carboxylic acid or a salt thereof; and a component selected from the group consisting of an alkaline earth metal ion, an alkali metal ion, a transition metal ion, an inorganic phosphate, molybdate ion, nitrate ion, nitrite ion, an azole compound, a copper and copper alloy corrosion inhibitor, a silicate, a silicate stabilizer, a water-soluble polymer, and combinations thereof. Ready-to-use heat transfer fluids and methods for preventing corrosion in heat transfer systems are described.