Corrosion and Electrochemical Behavior of A508III Low Alloy Steel in Boric Acid Solutions with Different Concentrations

The corrosion and electrochemical behavior of A508III low alloy steel in 0.05-0.5 mol/L H3BO3 solutions at 25 ℃ were studied by weight loss measurements and electrochemical measurements.Low open circuit potentials,low electrochemical impedance and high corrosion rates were observed in boric acid solutions of higher concentrations.Three levels of open circuit potentials,i.e.higher potentials (>-200 mV(SCE)),lower potentials (<-500 mV(SCE)),and intermediate potentials were observed in boric acid solutions of lower concentrations,where lower open circuit potentials corresponded to lower electrochemical impedance and higher open circuit potentials corresponded to higher electrochemical impedance.Anodic and cathodic polarization curves showed a linear relationship in a wide range of potential,which was related to the low conductivity of test solutions.The measured values of open circuit potentials,corrosion rates and the calculated E-pH diagrams were consistent.