Cr effect on FAC rate and its correlation with oxide layer characteristics

Authors : Yutaka Watanabe, Abe Hiroshi

Company : Tohoku University
Country : Japan

Topic :

Flow Accelerated Corrosion

ABSTRACT :

Combined effects of Cr content (~1 wt %) and environmental factors, pH and dissolved oxygen concentration, on removal rate of carbon steels due to flow accelerated corrosion have been examined by experiments. Cr content holds a strong impact on the FAC rate regardless of pH values from 6.84 to 10.4. Addition of 1% Cr to a carbon steel reduces the FAC rate by one order of magnitude under the environmental conditions, where magnetite forms. Detailed characterizations of oxide layer formed on the specimens have been carried out by using SEM and TEM. It has been suggested that characteristics of oxide layer were obviously different between low and high Cr content steels, and their correlation to the FAC rate has been discussed. Porous oxide monolayer has been observed on the low Cr content steels; in contrast dense oxide inner layer and outer layer which contains chromium much higher than base metal have been formed on the high Cr steels.