Size Effect of Copper Precipitation Particles on Electrochemical Nanoscopic Galvanic Behavior in Cu-Added Ultra Low Carbon Steel
Electrochemical polarization measurements were applied to Cu-added ultra low carbon steels aged at 773 K for duration ranging from 9×10 to 5×10<SUP>6</SUP> s to investigate size effect of copper precipitation particles on passivation of the steel. The anodic polarization curve measurements in 0.5 kmol/m<SUP>3</SUP> H<SUB>2</SUB>SO<SUB>4</SUB> solution revealed that the passive current density <I>I</I><SUB>pass</SUB> showed almost no variation until the aging process reached the overaged stage in which the Vickers hardness of the steel began to decrease. Thereafter, the <I>I</I><SUB>pass</SUB> increased monotonously with increasing aging time in the overaged stage. This increase in <I>I</I><SUB>pass</SUB> due to aging was considered to result from the preferential anodic dissolution of grown copper particles. Thus, the corrosion resistance of the Cu-added ultra low carbon steel scarcely deteriorated even if the size of copper particles increased with aging time before the maximum hardness was reached. These results reflected that there was a critical nanometer size of copper particles as a nanoscopic galvanic action beyond which a good protective passive film could not be formed.
- Materials transactions
Materials transactions 43(6), 1348-1351, 2002-06-01