Removal of niobium second phase particle deposits from pickled zirconium-niobium alloys
View Patent ↗The present invention provides a method for removing niobium-rich second-phase-particle (SPP) deposits from zirconium-niobium alloy components. The method comprises washing a freshly pickled and rinsed zirconium-niobium alloy component with an acidified oxalic acid or ammonium oxalate washing solution. The method of the present invention results in a rapid, efficient and complete removal of surface SPP deposits from the zirconium-niobium alloy component without pitting, leaving behind a clean, shiny surface without the need to use water blasting or mechanical wiping operations.
1. A method for removing niobium-rich second-phase-particle (SPP) deposits from a surface of a freshly pickled and rinsed zirconium-niobium alloy component, comprising washing the freshly pickled and rinsed zirconium-niobium alloy component with an acidified oxalic acid or an acidified ammonium oxalate washing solution to remove said niobium-rich second-phase-particle (SPP) deposits from the surface of said zirconium-niobium alloy component.
2. The method of claim 1 , wherein oxalic acid or ammonium oxalate is acidified with nitric acid.
3. The method of claim 1 , wherein the zirconium-niobium alloy component is washed in the washing solution for about 1 to 10 minutes.
4. The method of claim 1 , wherein the zirconium-niobium alloy component is washed in the washing solution for about 2 to 5 minutes.
5. The method of claim 1 , wherein the zirconium-niobium alloy component is washed in the washing solution having a temperature of about 26° C. for about 4 minutes.
6. The method of claim 1 , wherein waste solution of the washing solution is treated with calcium hydroxide to precipitate calcium oxalate.
7. The method of claim 2 , wherein a concentration of oxalic acid or ammonium oxalate in the washing solution ranges from between about 1.0 to 8.0 weight percent and the concentration of nitric acid in the washing solution ranges from between about 1.0 to 40.0 weight percent.
8. The method of claim 2 , wherein a concentration of oxalic acid or ammonium oxalate in the washing solution ranges from between about 2.5 to 5.0 weight percent and the concentration of nitric acid in the washing solution ranges from between about 5.0 to 10.0 weight percent.
9. The method of claim 2 , wherein a concentration of oxalic acid or ammonium oxalate in the washing solution is about 2.5 weight percent and a concentration of nitric acid in the washing solution is about 5 weight percent.