Buying a coated titanium anode is really buying a coating system. The titanium substrate is almost always the same TA1/TA2 material — what determines whether your anode lasts six months or six years is which precious-metal oxide (or platinum) sits on top of it, and whether that coating was matched to your electrolyte. This guide walks through the three coating families we manufacture and how to choose between them.
Start with your electrolyte, not the anode
Every coating family has an electrochemical “home turf”:
- Platinized (Pt) — the versatile precious-metal coating. Works in both oxygen- and chlorine-evolving environments, which is why it dominates decorative gold and rhodium plating, PCB gold-finger lines and small electrolytic water devices. Typical window: current density under 5,000 A/m², temperature under 80 °C, pH 1–12.
- Ru-Ir (ruthenium-iridium) — the chlorine-evolution specialist. Its low chlorine overpotential delivers high current efficiency in chlor-alkali cells, sodium hypochlorite generators and seawater electrolysis. Typical window: under 3,000 A/m², HCl under 20%.
- Ir-Ta (iridium-tantalum) — the oxygen-evolution specialist, and the toughest of the three in strong acid. The go-to coating for copper electrowinning, VCP / PCB plating lines, copper foil production and high-speed plating. Typical window: up to 10,000 A/m², H₂SO₄ up to 60%.
The five questions that decide your coating
When a customer sends us an inquiry, these are the parameters our engineers look at first — have them ready and you’ll get a useful recommendation in one email instead of five:
- Electrolyte composition — chloride, sulfate, cyanide-based gold bath, seawater, or pure water? Fluoride content matters too: above 50–500 mg/L (depending on coating) it attacks the titanium substrate.
- Current density — the single biggest driver of coating wear. Doubling current density can cut life by more than half.
- Temperature — all three families prefer under 60–80 °C; beyond that, life drops fast.
- Target service life — higher noble-metal loading (e.g. 45 g/m² vs 8 g/m²) buys life at higher upfront cost. Often the cheaper per-year choice.
- Geometry and connection — mesh, plate, tube or rod, plus tab position, decide how evenly current distributes in your tank.
A quick selection table
| Your process | Recommended coating | Why |
|---|---|---|
| Gold / rhodium decorative plating | Pt (1–5 μm) | Stable in cyanide gold baths, 3+ years bath life |
| Chlor-alkali / NaClO generation | Ru-Ir | Low Cl₂ overpotential, high efficiency |
| Seawater electrolysis | Ru-Ir | Purpose-built for chloride media |
| Copper foil / electrowinning | Ir-Ta | Survives strong sulfuric acid at high current |
| VCP / PCB plating lines | Ir-Ta | Long life in acid copper, recoatable |
| Hydrogen water & disinfection devices | Pt (0.2–5 μm) | Low-voltage stability, CAS124-tested |
| Au-Sn eutectic plating | Pt or Ir-Ta | Insoluble in Au-Sn chemistry |
Don’t forget the end of life
A DSA anode’s coating wears out; its titanium substrate usually doesn’t. Before you budget full replacements, ask your supplier about recoating — stripping and re-applying the coating typically costs a fraction of a new anode and can be repeated two to three times. Also ask for the accelerated life test data of the batch you’re buying (ours run at 0.5 mol/L H₂SO₄, 40 °C, 2.0 A/cm²) — it’s the only honest way to compare two suppliers’ coatings on paper.
Have your bath composition and current density at hand? Send them through our RFQ Configurator — we’ll come back with a coating recommendation and quotation within 24 hours.