Development of corrosion rate measuring apparatus for carbon steel under reducing environment

In order to monitor the corrosion rate of carbon steel under deep under-ground environment which is depleted with oxygen, the corrosion rate measuring apparatus using the hydrogen permeation current was developed. Inner surface of the carbon steel monitor electrode made of beverage can was coated with Ni or Pd-Ni plating, which was used as the hydrogen detecting electrode. Corrosion rate which was estimated from hydrogen permeation current well consisted with literature data. Corrosion rate in acidic solution at pH < 3.5 was found to be not changed with time, but the corrosion current in neutral and alkaline solution was decreased with time according to the parabolic rate law and approached the value below 0.01 μA/cm2 after long time elapsed. (author)