Effect of chloride ion on corrosion behavior of low carbon steel in 0.1 M NaHCO_3 solution with different dissolved oxygen concentrations

The corrosion behavior of low carbon steel in 0.1 M NaHCO_3+ 0.1 M NaCl solution with different dissolved oxygen concentrations was investigated with gravimetric tests and electrochemical measurements.Results show that the corrosion mass loss of steel is remarkably increased with the addition of chloride ion. In the initial stage, the carbon steel tends to active dissolution due to the dissolution effect of chloride ion on the oxide film; as a result, the corrosion potential maintains as low values. With the immersion time going by, the corrosion potential of the steel is promoted as a result of the accumulation of the corrosion products. However, the rust layer is loose and porous due to the deteriorating effect of chloride ion, which decreases the reduction resistance of oxygen. Meanwhile, the porous rust layer could be repaired by the depolarization of oxygen. Under the synergistic effect of chloride ion and oxygen, the corrosion of the steel is accelerated during the repeated process of dissolution and reparation of the oxide film.