“Coated titanium” covers two quite different jobs. In one, the coating is the working electrode surface, as in dimensionally stable anodes (DSA) used for hypochlorite generation, electroplating or electrochemical water treatment. In the other, a thin noble-metal layer sits on a titanium porous transport layer (PTL) in a PEM water electrolyzer, mainly to limit titanium passivation and contact resistance with the anode catalyst layer. Asking which coating to use only makes sense once you know which of these jobs the part is doing.
Why titanium needs a coating at all
Titanium resists corrosion in many anodic environments because it forms a protective oxide film. That same film is poorly conductive, so bare titanium used as an anode tends to passivate and its contact resistance rises. Reviews of the DSA story (Trasatti, 2000; Fu, 2024) describe putting a conductive, catalytically active and stable coating onto titanium. Early platinum-coated titanium chlorine anodes suffered from platinum wear and coating loss; the industrial breakthrough came with mixed metal oxide coatings such as RuO2–TiO2, applied by thermal decomposition. Iridium-oxide-based coatings are the usual family where oxygen evolution is the main anode reaction. Those historical notes explain the industry context; they are not a performance guarantee for any HuiRui coated part.
Job 1: coated titanium as the working anode
Typical uses include sodium hypochlorite generators, electroplating and electrowinning, and electrochemical wastewater treatment. Here the questions are about the anode reaction and the electrolyte:
- Which reaction dominates? Chlorine evolution and oxygen evolution favour different coating chemistries. Tell us the electrolyte, its chloride content, pH and temperature rather than only “iridium” or “platinum”.
- Current density and duty. Continuous operation, frequent shutdowns and polarity reversal all matter for how a coating is selected. State polarity reversal up front when it applies.
- Geometry. Woven or expanded titanium mesh is a common choice for flat or cylindrical anodes because it is easy to cut, roll and weld to a current lead. Titanium foam or felt offers more internal surface but is harder to clean and to keep fully wetted, so it suits flow-through or compact designs more than open tanks.
Job 2: coated titanium PTLs in PEM electrolyzers
In PEM cells the anode PTL is usually titanium felt, sintered titanium or titanium foam, and published protective coatings are often very thin. Public papers give a useful picture of the research landscape:
- Liu et al. (Electrochemistry Communications, 2018) reported that sputtering a thin iridium layer onto commercial titanium PTLs lowered the PTL/catalyst-layer interface resistance and, in their cells, brought performance close to carbon-based PTLs.
- Chang Liu’s RWTH Aachen doctoral thesis (2021) on noble-metal-coated PTLs reported that about 20–50 nm Ir or Pt coatings reduced contact resistance in that work, and that Ir loading on one side could be cut to about 0.025 mg/cm2 without losing cell performance in that study.
- Srour et al. (International Journal of Hydrogen Energy, 2024) compared Pt, Au and Ir coatings: Pt gave the best beginning-of-life performance in their tests, while a 10 nm Ir coating showed the best durability under start/stop cycling; Au dissolved and redeposited.
These are results from specific cells and test protocols, not guarantees for every stack and not HuiRui product claims. The practical takeaway is that coating choice on a PTL depends on how the electrolyzer will be operated—including how often it is started and stopped—and that thickness, coverage and which face is coated should be agreed explicitly per enquiry.
Mesh, foam or felt: matching the substrate
| Substrate | Where it tends to fit | What to specify |
|---|---|---|
| Titanium woven or expanded mesh | Working anodes in tanks and cells; supports and current distributors | Mesh count or opening, wire diameter, sheet size, flatness, lead/welding needs |
| Titanium foam | Compact or flow-through electrodes; some PTL and gas diffusion designs | Thickness, pore size (PPI), porosity, and whether thickness is free or compressed if your drawing already states it |
| Titanium fiber felt | PEM anode PTLs; high-surface flow-through electrodes | Thickness, porosity, fiber diameter if known, surface finish on the catalyst side, any compression notes already on the drawing |
For the substrate itself, see our guides on titanium woven wire mesh mesh count and wire diameter, titanium fiber felt porosity and thickness for PEM projects and titanium felt pore size, flow and PTL contact. If you are still choosing the electrolyzer technology, our overview of ALK, PEM, AEM and SOEC electrolyzers explains where titanium parts are used and where nickel is the usual choice. Those pages cover substrate specification; they do not replace a coating discussion.
Questions to settle before ordering
You do not need a complete laboratory list to contact HuiRui. Share the application, approximate size, a sketch or a drawing first. The items below help when you already have them:
- Is the coated part a working anode or a PTL/current collector?
- Electrolyte, temperature, current density, and whether polarity reversal or frequent shutdown occurs.
- Coating type requested (Ir-based, Pt, or mixed metal oxide), any target loading or thickness already defined by the project, and whether one face or both faces are coated.
- Substrate form and dimensions, plus any cutting, edge treatment or welded tabs.
- How coating will be checked on delivery (for example a thickness or loading measurement method already required by the project) and whether samples are needed before a batch.
We supply iridium coated titanium mesh, iridium coated titanium foam, iridium coated titanium felt, platinum coated titanium mesh, platinum coated titanium foam and platinum coated titanium felt, as well as uncoated titanium fiber felt and titanium wire mesh. Coating details and dimensions are confirmed per enquiry. Product pages may list illustrative ranges for quotation discussion; do not treat published literature results, illustrative ranges, service-life wording or case-style claims as verified stack performance for every design. Send your drawing and the operating conditions above, and we will reply with what we can make.
References
- S. Trasatti, “Electrocatalysis: understanding the success of DSA®”, Electrochimica Acta 45 (2000) 2377–2385. https://doi.org/10.1016/S0013-4686(00)00338-8
- X. Fu, “What insights can we learn from dimensionally stable anodes (DSAs)?”, Carbon Future (2024). https://doi.org/10.26599/CF.2024.9200027
- C. Liu et al., “Performance enhancement of PEM electrolyzers through iridium-coated titanium porous transport layers”, Electrochemistry Communications 97 (2018) 96–99. https://doi.org/10.1016/j.elecom.2018.10.021
- C. Liu, “Noble metal coated porous transport layers for polymer electrolyte membrane water electrolysis”, doctoral thesis, RWTH Aachen University / Forschungszentrum Jülich, 2021. Record: https://publications.rwth-aachen.de/record/822403 (open PDF mirror used for verification: Universitäts- und Landesbibliothek Bonn).
- T. Srour et al., “On the contact resistance between the anode and the porous transport layer in a proton exchange membrane water electrolyzer”, International Journal of Hydrogen Energy 58 (2024) 351–361. https://doi.org/10.1016/j.ijhydene.2024.01.134