Comparison of General Corrosion Behavior between Domestic and Imported Alloy 690TT Heat-Exchanger Tubes

Metallographic and microstructure of domestic and imported 690TT alloy heat transfer tube materials were analyzed and compared. After confirming that the microstructure difference between the two was not obvious, the open circuit potential and weak polarization curves of the two tube samples under 5 μg/L and 100 μg/L dissolved oxygen (DO) conditions were measured in a simulated nuclear power plant's high temperature and high pressure primary circuit water environment(300℃, 10 MPa, 1 200 mg/L B, 2.2 mg/L Li). The average corrosion rate (v_corr) was calculated by testing the electrochemical dynamic parameter J_corr in the corrosion process. The results showed that when DO<5 μg/L, the average corrosion rates of domestic and imported tube were 0.68 μm/a and 0.71 μm/a, respectively; when DO was 100 μg/L, the average corrosion rates were 0.81 μm/a and 0.85 μm/a, respectively. Dissolved oxygen would promote the corrosion of the alloy, but the average corrosion rates of domestic and imported tube under the test conditions were very low, and the general corrosion characters were almost the same.