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Anodic dissolution of chromium at high current densities in sodium nitrate electrolyte

: Schneider, Michael; Simunkova, Lenka; Manko, Michal; Lohrengel, M.M.; Hoogsteen, W.


Journal of solid state electrochemistry 23 (2019), Nr.2, S.345-350
ISSN: 1432-8488
ISSN: 1433-0768
Fraunhofer IKTS ()
anodic dissolution; electrochemical machining; chromium; oxygen efficiency; ECM

The dissolution mechanism of pure chromium at high current density characteristic for electrochemical machining processes is studied. The combination of electrochemical, microscopic, and spectroscopic techniques leads to a comprehensive interpretation of the dissolution mechanism. The polishing quality increases with increasing nitrate concentration and current density, respectively. The oxygen evolution amounts up to 45% of the consumed anodic charge and the apparent valence of the chromium dissolution decreases with increasing applied potential down to z = 3.5. The authors explain this phenomenon by a passive dissolution of chromium via Cr3+ followed by a chemical oxidation of Cr3+ to dichromate under nitrate reduction to nitrogen.