The influence of dissolved oxygen concentration on the corrosion behavior of AK12M2 alloy in solutions simulating the operating conditions of heating radiators

• Corrosion of the AK12M2 alloy proceeds from a passive state at 90°C and dissolved oxygen concentrations less than 0.12 ppm in weakly alkaline model solutions simulating the heat carrier. • A dark grey composite film based on Si and SiO 2 is formed due to the preferential dissolution of aluminum from the AK12M2 alloy. • At 90°C and dissolved oxygen concentrations of 1.8, 0.12 ppm in model electrolytes, in addition to aluminum etching, ulcer corrosion occurs on the AK12M2 alloy. • The difference between the breakdown potential of the passive film and the open circuit potential indicates the probability of ulcer formation on AK12M2 alloy. The type and mechanism of corrosion damage to AK12M2 alloy, which is used to manufacture heating radiators, in model solutions simulating the heat carrier at various concentrations of dissolved oxygen and a temperature of 90°C have been studied. It has been found that with long-term exposure of the AK12M2 alloy in weakly alkaline (pH 8.3; 9.5) electrolytes at 90°C and dissolved oxygen concentrations of 1.8; 0.12 ppm, ulcer corrosion and preferential etching of aluminum from the alloy occur. It has been shown that at dissolved oxygen concentrations of 0.12 and 0.04 ppm and in deoxygenated model solutions, preferential dissolution of aluminum occurs, though a passive film is present on AK12M2 alloy. In this case, a dark gray composite film is formed on the surface of this layer, which primarily consists of silicon and its compounds. For an accelerated assessment of the probability of corrosion ulcer formation, polarization curves were recorded, and the ulcer resistance basis was used, which is the difference between the potential of passive state breakdown on alloy and its open circuit potential. The greater the ulcer resistance basis, the lower the probability of ulcer formation on AK12M2 alloy. The greatest ulcer resistance basis is observed at dissolved oxygen concentrations no higher than 0.04 ppm. Thus, the conditions for long-term fault-free operation of heating radiators at these oxygen concentrations in model electrolytes at a maximum temperature of 90°C have been determined.