Chisinau tap water by the chemical composition is medium or moderately hard. As the total content of chloride and sulfate ions (more 150 mg/l), it relates to a highly aggressive medium. The SO42¯ ions caused a common, relatively uniform corrosion. However, on the inner surface of pipes can be formed the pitting due to the presence in the water of activating chlorine ions, which in some cases may be through, which leads to an emergency. Moreover, the ionized iron by passing into the water, are accumulates there to deteriorate its quality. It is known to use as a corrosion inhibitor carboxylic acids or their salts. By us, was used α-ketoglutaric acid HOOC-C(=O)CH2-CH2-COOH with a concentration of 0.05-0.75 g/l. In this case, the corrosion loss of metal is reduced by more than 7 times, providing a degree of protection Z = 87,8 % at a concentration of 0,25 g/l and a test duration of 72 hours. It should be noted, that is observed a slight difference in the values of the parameters of inhibiting of steels in the corrosion medium from the holding time that says about the stability of the inhibitor. In the process of corrosion, the pH of medium is slightly basified with increasing the time of tests of samples. Thus, the higher the concentration of the inhibitor, the more anodic potential shifts to the positive side, which indicates about the difficulty of the of ionization process of the metal. Addition of inhibitor in the corrosion medium shifts the stationary potential of the de-energized electrode in the negative side that says that the inhibitor is the inhibitor of cathodic action. Thus, was developed an environmentally safe and convenient to operate inhibitor of corrosion of steel in hydraulic structures, where the medium is natural water.