How Polarity Reversal Affect the Lifetime Of Ruthenium and Iridium Tantalum Coated Titanium Anodes

How Polarity Reversal Affect the Lifetime Of Ruthenium and Iridium Tantalum Coated Titanium Anodes

The current density, sodium chloride concentration, and current reversal cycle length can affect the polarity reversal of coated titanium electrodes.
 
For ruthenium and iridium tantalum coated titanium anodes, the lifetime increased with decreasing current density or decreasing reversal cycle frequency. NaCl had no effect on lifetime over the 180 range studied. The effect of anodic and cathodic current density indicated that if either was decreased to 200 A/m2, lifetimes became very long (> 1 week). In general, ruthenium coated titanium anodes have longer lifetimes than iridium tantalum coated titanium anodes during current reversal.

Sodium anion compositional and concentration changes had a varying extent of influence on coated titanium anodes life in the five anions examined under current reversal electrolysis. Iridium tantalum coated titanium anodes had longer lifetimes in nitrate anions, and the service life of iridium tantalum increased as a function of nitrate concentration. Ruthenium coated titanium anodes had longer lifetimes in the remaining four anions. Its life increased with increasing hydrogen phosphate concentration. The lifetime of both anodes seemed to decrease as a function of carbonate ions. The lifetime of the anodes appeared not to change or only slightly decreased as a function of either perchlorate or sulfate anions.


The response of the coated titanium electrodes to three sodium electrolytes in the presence of hard water was determined. The lifetime of iridium tantalum coated titanium anodes was determined to be higher than ruthenium coated titanium anodes in nitrate and hard water. Electrolyte and hard water concentration and compositional changes affected iridium tantalum coated titanium anodes life more than ruthenium coated titanium anodes under all the water hardness examined, except in calcium and nitrate ions. In the presence of nitrate, increasing calcium concentration did not affect iridium tantalum coated titanium anodes life. Ruthenium coated titanium anodes had longer lifetimes than Iridium tantalum coated titanium anodes in hydrogen phosphate and perchlorate in the presence of calcium and magnesium. However, ruthenium coated titanium anodes life in these electrolytes appeared to have been influenced by anion concentration and compositional changes than by calcium and magnesium concentration and compositional changes.