Evaluation of Corrosion Rate by Surface Observation of Carbon Cement

The immersion test of carbon cement containing furan or phenol resin was conducted for 20 hours in 40% H2SO4-2% HCl solutions with different amounts of HNO3 at 120°C. The corrosion behavior was evaluated by the ratio of dark area to the total area of a replica film obtained from the corroded surface of carbon cement which was polished before immersion test. The replica was observed by using an image analyser. It was found that carbon cement was attacked by the test solution when the content of HNO3 was higher than 0.1%. Then the ratio of dark area of the replica became about 50% from the initial value 14% for phenol cement. It is concluded that the image analysis method of measuring the ratio of dark area of the replica is feasible to evaluate the corrosion rate of carbon cement in corrosive solutions.