回転電極による鋼管の腐食速度予測

抄録

The effects of fluid flow on the corrosion rate of pipes and tubes were studied with rotating disk electrode and a prediction method for corrosion rate was proposed. Polarization curves in both N₂-purged and CO₂-saturated NaCl solution were depolarized with the increase of angular velocity showing the increase of limiting current density and corrosion current density. The limiting current density increased linearly as a function of the square root of angular velocity which shows the rate determining process is the diffusion of H⁺ ion to the electrode surface. Another possibility contributing the rate determining process is the CO₂ hydration reaction to H₂CO₃. The corrosion current density also increased as a function of square root of rotating velocity following the theoretical solution. Using the similarity solutions obtained for mass transfer with pipe flow and rotating disk electrode, the rotating velocity was converted to the equivalent velocity in pipe. On that basis the corrosion rate of pipe was equal to the corrosion rate of the rotating disk electrode. The corrosion rate of rotating disk electrode obtained by the electrochemical method was used to predict the corrosion rate of the pipe at the equivalent velocity.