Effect of Alternating Current Frequency on Corrosion Behavior of X65 Steel in CO₃^2-/HCO₃^- Solution

Effect of alternating current (AC) frequency (30-1000Hz) on corrosion behavior of X65 steel in concentrated carbonate/bicarbonate solution was studied by potentiodynamic polarization curve measurements, immersion tests and surface characterization technique. The results show that in the range of 30-1000Hz, except 200Hz, at low AC frequency (≤ 300Hz), as AC frequency decreases, the passivation region become obviously narrow, the broken potential of pitting corrosion shifts negatively, the passive current density increases and the critical passivation current density increases; at high AC frequency (> 300Hz), frequency has a slight effect on the passivity of X65 steel. The corrosion rates of X65 steel decrease with the AC frequency increase, at low AC frequency, the corrosion rates of X65 steel decrease rapidly as AC frequency increases, while at high AC frequency, the corrosion rates decrease slightly as AC frequency increases.