Electrodissolution studies of 304 stainless steel in sodium nitrate electrolyte

Technical Report · Mon Dec 01 04:00:00 EST 1997

DOI:https://doi.org/10.2172/573283· OSTI ID:573283

Weisbrod, K R; Trujillo, V L; Martinez, H E

To explore the impact of a wide range of operating parameters upon 304 stainless steel (SS) dissolution in sodium nitrate (NaNO{sub 3}) electrolyte, the staff of Engineering Science Applications-Energy and Process Engineering performed a series of beaker experiments. The variables that the authors explored included NaNO{sub 3} concentration, chromate concentration, pH, stirring rate, and current density. They adjusted the run length to obtain approximately 10 mg/cm{sup 2} metal removal so that they could compare surface finishes under similar test conditions. Key findings may be summarized as follows. Current efficiency during dissolution depends most strongly upon current density and electrolyte concentration. At 0.05 A/cm{sup 2}, current density is more dependent upon chromium concentration than they previously thought. They obtained the best surface finish in a classical electropolishing regime at current densities above 1.5 A/cm{sup 2}. Mirror-like finishes were obtained at near 100% current efficiency. At 0.05 a/cm{sup 2} they obtained reasonable surface finishes, particularly at lower electrolyte concentration. Current efficiency was low (30%). At intermediate current densities, they obtained the worst surface finishes, that is, surfaces with severe pitting. Also, they explored preferential attack of the weld zone during electrodissolution of 304 stainless steel cans. Electrodissolution removed approximately twice as much material from cans with unshielded weld zones as from cans with shielded weld zones. The following implications are apparent. While operation above 1 A/cm{sup 2} yields the best surface finish at 100% current efficiency, equipment size and power feedthrough limitations reduce the attractiveness of this option. Because other Los Alamos researchers, obtained more favorable results with the sulfate electrolyte, the authors recommend no further work for the sodium nitrate electrolyte system.

• Research Organization: Los Alamos National Lab., NM (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 573283
• Report Number(s): LA--13225-MS; ON: DE98003068
• Country of Publication: United States
• Language: English

Related Subjects

05 NUCLEAR FUELS
DECONTAMINATION
DISSOLUTION
ELECTROLYSIS
GLOVEBOXES
SODIUM NITRATES
STAINLESS STEEL-304
SURFACE CLEANING
WELDED JOINTS