Relationship Between the Occurrence of Pitting Corrosion and Amount of Residual Carbon by Accelerated Testing of Copper Tubes

Abstract

Residual carbon on the inner surface of copper tubes is one of the causes of pitting corrosion. In evaluation tests of pitting corrosion resistance, the original pipes used in actual equipment were applied for the test specimens. The occurrence of micro–mounds on the inner surface of specimen was investigated after the short time filling test using special solution mixed with various ratios of factors that promote or inhibit corrosion. As the result, it was found that the pitting corrosion resistance should be evaluated by the number of occurrence of micro–mounds in size of 50 to 400 μm under the concentration of corrosive anion at 100 mg/L in special solution. In addition, differences in the amount of residual carbon caused differences in the occurrence of micro–mounds and the form of corrosion over time was differed due to the differences in the amount of residual carbon. It was concluded that this test in a short time should be useful to evaluate the pitting corrosion resistance of copper tubes.