Due to their superior corrosion resistance, Titanium and Ti-Pd alloys are widely used as a substrate for Dimensionally Stable Anode (DSA) construction across numerous applications. However, Titanium is not always corrosion resistant enough to sustain long life and may need to be repaired or replaced to hydrogen embrittlement and subsequent hydride cracking that occurs over the life of an anode. Hydrogen is most often generated due to under-deposit corrosion, which is a type of crevice corrosion, beneath electrocatalytic coats like Platinum and Mixed Metal Oxide (MMO). The hydrogen is absorbed into the Titanium over time which causes embrittlement and eventual precipitation of titanium hydrides that can lead to cracking of the anode
Coupled with the problem that Titanium is not highly electrically conductive, and rather insulating for metals, an alternative material should be considered to achieve lower life-cycle costs. Niobium is a natural next step, as it is more crevice corrosion-resistant and more electrically conductive compared to Titanium. Tantalum is also an upgrade to Titanium for DSA’s, albeit at a much higher cost than Niobium.
A few examples of current DSA applications where Niobium is used as a higher-performance alternative to Titanium due to its higher corrosion resistance, higher conductivity, improved reliability, and lower life cycle costs include:
Hard Chrome Plating
- Platinized Titanium and Niobium anodes for chrome plating are completely or partially covered with a few microns of platinum (usually 2.5µm).
- Mesh anodes provide very efficient use of platinum and are available with a surface factor of 0.5-2.3 dm2.
- In fluoride-containing baths, and at current densities >75 A/dm2 platinized Niobium is preferred for long life and plating efficiency.
Cathodic Protection Anodes
- Niobium is used as an anode for the cathodic protection of pipelines.
- The Nb2O5 film has a high electrochemical breakdown potential.
- Platinized Niobium anodes are effective in low-conductivity soils.
- The breakdown voltage of Nb2O5 film is ~120 volts in most cathodic protection environments.
When to Upgrade from Titanium to Niobium for Dimensionally Stable Anodes (DSA’s)
- Where operating voltages are relatively high, Niobium- and Tantalum-based anodes are generally selected.
- Titanium is less expensive; however, in seawater, the recommended operating voltage of platinized Titanium anodes is only 8V.
- The breakdown voltage of Niobium oxide film is approximately 120 volts in most cathodic protection environments.
- Niobium has an electrochemical breakdown potential >10X higher than Titanium.
- Niobium anodes are >3-5x more conductive than Titanium and provide higher electrical efficiencies.
If you desire higher-performing, more reliable, and longer-lasting alternatives to Titanium anodes for your applications, please consider requesting a consultation with the experts at Niobium Research LLC today.