Why Titanium is Used as the Substrate of Dimensionally Stable Anodes

Why Titanium is Used as the Substrate of Dimensionally Stable Anodes?

Titanium is commonly used as the substrate material for dimensionally stable anodes because it is not easily dissolved under anodic polarization in aqueous environments. The stability of titanium can be attributed to the compact oxide film that forms on its surface. This film forms naturally in the air, but forms more rapidly when the metal is polarized to an anodic potential in an aqueous electrolyte. Using titanium as the substrate for a DSA increases the electrodes stablilty because if the substrate is exposed it will not readily dissolve; however, it will oxidize, increasing the thickness of the oxide layer on the surface. The resulting oxide (TiO2) has a high resistivity compared to conductors such as copper or gold.

As the oxide layer gets thicker, the resistance R increases following the equation:
R=ρl/A

Where
R ≡ resistance (ohms)
ρ ≡ electrical resistivity (ohm cm)
l ≡ thickness of the conductor (cm)
A ≡ cross sectional area (cm2
)
If the electrode is being operated at a specified current density and the area is fixed then the
potential increases following the equation:
(7) V=I.R
Where
V ≡ potential (volts)
Ι ≡ current (amps)
R ≡ resistance (ohms)
This increase in the voltage speeds up the oxidation reaction, further increasing the thickness.
Eventually the electrode is deemed ‘deactivated’ because it is no longer efficient to continue the electrolysis. It is inefficient because energy is being wasted in the oxidation of titanium
and the evolution of heat that could be better used to generate electrochemical disinfectants.