Abstract
The effect of dissolved oxygen on carbon steel corrosion was investigated by immersion tests in a circulating loop, and by measurement of polarization resistance using rotating cylindrical electrodes. Carbon steel is easily passivated by dissolved oxygen in flowing pure water (specific conductivity <0.5μΩ/cm) at room temperature, indicating that the effect of water flow velocity is very remarkable. Passivated steel begins to corrode, if dissolved oxygen is removed from the water or flow is stopped even in the presence of dissolved oxygen. Under such conditions, corrosion intiates locally at weak points of the surface film, and the pits grow gradually and then general corrosion occurs. Once steel has been passivated by oxygen, the passive state can be maintained under a slow water velocity with oxygen rich condition. Even if steel is corroding, it can be passivated easily by the addition of oxygen together with water flow. This phenomenon is reproducible and seems to have a practical significance.
