Lab-Scale Electrochemical Cell (25 L, Pb Cathode) for Anodization and Polishing, EAPLSEC

A lab-scale electrochemical cell for anodization and electropolishing (EP) is designed to perform high-voltage dielectric oxide growth or controlled anodic dissolution on valve metals (Al, Ti, Zr, Nb, Ta) and alloys (stainless steel, Nitinol, Co-Cr).Both processes treat the workpiece as the anode, but they operate under divergent electrochemical regimes: electropolishing drives mass-transport-limited leveling and micro-smoothing, whereas anodization drives field-assisted oxide growth and self-assembled nanopore/nanotube formation.

Regarding the anodization window: Operates either in the barrier-type regime (neutral electrolytes like ammonium borate, forming thin non-porous dielectric films) or the porous/nanotubular regime (acidic electrolytes like oxalic, sulfuric, or fluoride-containing organic mixtures). High-field ionic conduction grows the oxide (A}^{3+} + O^{2-} to Al2O3), while field-assisted chemical dissolution etches the pore bottoms.

Regarding the electropolishing (EP) window: Must be maintained on the mass-transport-limited plateau (j_lim). A viscous, high-resistance boundary layer (salt film / acceptor-depleted layer) forms over the surface. Protrusions and micro-asperities experience a steeper concentration gradient and dissolve faster than recessed valleys, yielding a mirror finish.

References:

1. C. C. Chen, et al. Electrochemical characteristics of surface of titanium formed by electrolytic polishing and anodizing, Journal of Materials Science, 2005, 40, 4053-4059. 
2. A. Acquesta, et. al., The Electropolishing of Additively Manufactured Parts in Titanium: State of the Art, Advanced Engineering Materials, 2021, 23, 2100545