In Situ Observation of Preferential Anodic Dissolution of Phosphorus Compound in Fe-P Alloys Using Raman Spectroscopy
The solution chemistry of P in the Fe-P alloy electrodes containing P of 0.104, 0.028, and 0.004 mass% has been investigated by using <i>in situ</i> Raman spectroscopy in an electrochemical cell under controlled potential in 0.1 kmol·m<sup>-3</sup> NaOH at 25°C. It is found that the segregation site of the precipitate with the chemical composition of F<sub>3</sub>P dissolves preferentially. Using <i>in situ</i> Raman spectroscopy three dissolution species of PO<SUB>4</SUB><SUP>3-</SUP>, HPO<SUB>4</SUB><SUP>2-</SUP>, and H<sub>2</sub>PO<SUB>4</SUB><SUP>-</SUP> were detected on the surface at the segregation site, and these concentrations depend on the location of the precipitate of P compound whether at grain boundary or in grain. The detection of HPO<SUB>4</SUB><SUP>2-</SUP> and H<sub>2</sub>PO<SUB>4</SUB><SUP>-</SUP> both of which are unstable in the solution of NaOH suggests that the localized corrosion at the segregation site of P induces decrease of pH.
- ISIJ international
ISIJ international 37(3), 278-282, 1997-03-15
The Iron and Steel Institute of Japan