Abstract: The oxygenated treatment experiments are carried out in the high-pressure feedwater system of the once-through boilers for 1 000-MW and 600-MW supercritical units to study the feasibility of inhibiting corrosion in the feedwater system by low-oxygen treatment (oxygen mass concentration <30 μg/L). The low-oxygen feedwater treatment experiments are conducted for the feedwater system separately when and after the passivation film is formed,. The results show that the amount of oxygen added to the feedwater must be kept at a higher levelduring the passivation film formation. Once the passivation film comes out, it can stay long and stable with the oxygen mass concentration ranging between 10 and 20 μg/L for the protection of the feedwater system. Aiming at inhibiting the corrosion of draining systems, the pH value of the feedwater should be maintained above 9.3 when the low-oxygen treatment is applied.

Key words: once-through boiler, feedwater, oxygenated treatment, low-oxygen treatment, passivation film