Plasma Electrolytic Nitriding Coating for Heat Exchangers: Advancing Surface Engineering

By Dr Ian Fordyce, Head of R&D, Conflux

In metal additive manufacturing, surface engineering often plays catch-up to innovation in design and production. Here at Conflux, we’re deeply committed to pushing the boundaries of what’s possible in both the structures we create, and in how we enhance them. Conflux’s latest R&D breakthrough is a game-changing surface treatment: Plasma Electrolytic Nitriding (PEN) coating.

This promising advancement secured significant support through the Australian Research Council’s Linkage Projects grant scheme. Initially pioneered at Deakin University and now progressing at RMIT University, PEN is set to deliver rapid, energy-efficient, and highly effective protection for 3D-printed metals.

Raising the Bar: Why Heat Exchanger Coating Improvement is Essential

Traditional post-processing coatings, like anodizing or even Plasma Electrolytic Oxidation (PEO), have clear limitations, especially when applied to intricate 3D-printed geometries. In high-silicon aluminium alloys (which are often used in additive manufacturing), anodization struggles with uniformity and adhesion. More importantly, it can’t reach internal channels or microfins without risking clogging or loss of performance.

PEN is our response to those limitations. It builds on the core science of PEO but goes a step further, introducing nitrogen into the equation to form a dense, thin layer of metal nitrides. This layer significantly boosts corrosion resistance, surface hardness, and wear resistance without sacrificing thermal conductivity. And crucially, it can be applied precisely and quickly.

SEM (Scanning Electron Microscope) image of Conflux PEN coating on complex AM-built geometries. PEN coating has strong adhesion to complex features, regardless of size.

What Is Plasma Electrolytic Nitriding Coating?

Plasma Electrolytic Nitriding uses high-voltage plasma discharge in a nitrogen-containing electrolyte to introduce nitrogen ions into the surface of metals. The result is a ceramic-like nitride layer just 2–5 microns thick. This is thin enough not to block internal features, but dense enough to dramatically enhance corrosion resistance.

This is particularly important for items like Conflux’s high-performance heat exchangers that contain ultra-thin walls or dense fin arrays within. With PEN, we can maintain the integrity of internal flow paths while protecting external surfaces from corrosion, erosion, and mechanical wear.

How Can Plasma Electrolytic Nitriding Enhance Freedom of Material Choice in Heat Exchangers?

Material choice is a critical aspect of any heat exchanger design and manufacture. Aluminium has long been a popular choice in AM, due to its availability, flexibility and manufacturability. For heat exchangers it offers excellent thermal conductivity, a high performance-to-mass ratio, cost-effectiveness and is lightweight. These qualities make aluminium alloys popular in Aerospace, Automotive, EVs and Industrial applications.

The benefit of PEN Coating is that it allows aluminium and other alloys to increase their corrosion resistance, durability and extend their working life.   This opens the door to a broader range of potential materials to be chosen for heat exchanger applications. For heat exchangers that demand internal cleanliness, external durability combined with long-term reliability, the results are very promising.  This also speaks to the expansion of potential applications for aluminium-based AM heat exchangers, previously unsuited to harsh environments.

Close up showing how the PEN creates a surface coating barrier between the Aluminium part/substrate and gas/fluid.

What Are The Key Benefits of Plasma Electrolytic Nitriding Coating?

• Superior Corrosion Resistance: PEN outperforms both anodizing and standard PEO, especially in harsh thermal or chemical environments.
• Increased Surface Hardness and Wear Resistance: The nitride layer enhances component durability without altering base geometry.
• Fast, Efficient Processing: PEN coatings form in minutes, with lower chemical use and energy input than conventional methods.
• Wider Alloy Compatibility: Works on alloys unsuitable for anodizing, which broadens the design and material choices for engineers.
• Environmentally Considerate: Uses fewer hazardous chemicals, supporting sustainable manufacturing goals.

Why Plasma Electrolytic Nitriding Coating is a Strategic Leap in Delivering Value for our Customers

This technology is tuned for high-value, high-performance components, especially those in the aerospace, automotive, energy and defense industries. As an R&D project, it aligns with Conflux’s system-level thinking: better surfaces mean better thermal performance, longer life cycles, and greater design freedom. PEN coating is more than a technical advancement, it’s part of Conflux’s drive to deliver greater value for our customers through long-lasting, higher-performing components, reduced maintenance and lower total cost of ownership.

For engineers, PEN offers a new lever to pull in the race toward reliability and optimisation. For our team, it’s part of our culture and commitment to continually innovate and push the cutting edge in heat exchange technology.

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