2010 Volume 59 Issue 7 Pages 265-271
Corrosion acceleration mechanisms of carbon steel pipes exposed in boiler water circumstances of power generation and chemical plants are not necessarily clarified, because of complicated degradations with chemical and mechanical actions caused under flow conditions. In order to clear basic corrosion phenomena of carbon steel in the high temperature water, corrosion batch tests using a small container for 24 hours and longer test duration were conducted up to a temperature of 463 K under stagnant and flow (agitated) conditions. Carbon steel specimens were weighed before and after a corrosion test, and after an electric removal treatment of iron oxide formed on test surfaces. The iron mass in oxide film and the dissolved iron mass in the solution were separated from the total corrosion loss of carbon steel. As results, it is found that the dissolution of iron from a carbon steel surface was predominant accompanying with the maximum mass loss of the specimens at temperatures of 373 to 393 K under stagnant and flow conditions. The total corrosion loss was increasing with testing time in spite of a formation of magnetite films on carbon steel surfaces. The flow condition in the case of this study was found to accelerate the dissolution of iron. An initial corrosion mechanism of carbon steel in the high temperature water was proposed according to the test results.
