The Hidden Risks of Material Compatibility in Data Center Liquid Cooling

As data centers scale to support AI and high-performance computing, liquid cooling has moved from optional to essential. Systems like CDUs, direct-to-chip loops, and immersion tanks now operate under tighter thermal tolerances and higher reliability expectations than ever before.

In this environment, material compatibility is not just a design detail. When wetted materials don’t align with the cooling medium, the impact is rarely immediate. Instead, it shows up over time: seal degradation, corrosion, sensor drift, or fouling. These issues are difficult to detect early, but can ultimately affect uptime, maintenance intervals, and total cost of ownership.

A More Complex Fluid Environment Than It Appears

At a glance, most liquid cooling systems rely on familiar fluids—water-glycol mixtures, refrigerants, or dielectric fluids. In practice, each of these comes with variations in additives, operating conditions, and long-term behavior.

• Water-glycol(PG25, PG55) remains the standard for CDU and secondary loops
• HFC and HFO refrigerants dominate primary cooling systems
• Dielectric fluids are expanding rapidly in immersion and advanced direct cooling

The nuance lies in formulation. Additives for corrosion control, biological stability, and thermal performance can significantly influence how materials behave over time. That’s why compatibility decisions should always be tied to the specific fluid and not just the category.

Material Compatibility at a Glance

The table below reflects common field experience aligned with ASHRAE TC 9.9 guidance:

Download the material compatibility chart

Where Compatibility Impacts Real System Performance

Material selection becomes most critical at sensing and control points throughout the cooling loop.

Level Monitoring in CDU Reservoirs

Reservoir level sensing must remain stable despite coating, additives, and fluid motion. In these applications, non-mechanical sensing technologies tend to perform best over time.

• Capacitive sensors like the CAP-300 are well-suited for coated or dynamic environments, where fluid movement or residue may be present
• Electro-optic sensors such as the ELS-1100 provide compact, repeatable point-level detection in clean, stable loops
• For higher durability requirements, designs like the ELS-1150 extend performance in more demanding conditions

These solutions typically rely on stainless steel housings and chemically stable polymers, helping maintain accuracy with minimal maintenance.

Pressure Monitoring Across Loops and Components

Pressure sensors are continuously exposed to fluid conditions, making material selection critical for long-term stability.

• Platforms like the 3100 Series and 3510 Series utilize stainless steel wetted parts, aligning well with glycol and refrigerant-based systems

• Wet-to-wet differential sensors such as the Setra Model 230 with a stainless steel diaphragm, are commonly applied across filters, pumps, and heat exchangers

In these locations, corrosion resistance and mechanical integrity directly influence measurement accuracy and system protection.

Flow Monitoring in Cooling Circuits

Flow measurement plays a key role in validating system performance and redundancy. Material compatibility here extends beyond the housing to internal components.

• Inline paddlewheel designs like RotorFlow® use composite rotors, ceramic pins, and stable wetted materials for durability

• For applications where fluid uncertainty or contamination risk is a concern, non-contact technologies like the XFT clamp-on ultrasonic flow meter eliminate wetted material exposure altogether

This shift toward non-contact sensing is gaining traction in high-value or rapidly evolving cooling architectures.

Fluid Control and Isolation

Valves are often overlooked in compatibility discussions, but they introduce critical elastomer considerations.

• Solenoid platforms such as the AG, BG, and DG Series rely on proper seal selection (e.g., FKM, Nitrile, EPR) matched to the fluid and temperature range

Even minor mismatches at this level can lead to leakage or reduced service life, particularly in systems with aggressive additives or elevated temperatures.

Designing for Reliability as Systems Evolve

One of the challenges engineers face today is that liquid cooling is not standardized. Systems vary by architecture, geography, and even operator preference.

That variability increases the importance of:

• Validating materials against exact fluid formulations
• Considering long-term exposure effects, not just initial compatibility
• Using proven materials in critical sensing locations
• Leveraging non-contact measurement where possible to reduce risk

As new fluids and cooling strategies continue to emerge, these practices help maintain consistency and reduce unexpected failure modes.

Why This Matters Now

The growth of liquid cooling is accelerating, driven by AI workloads and increasing rack densities. At the same time, operators are under pressure to scale quickly while maintaining uptime and efficiency.

Material compatibility sits at the intersection of those goals. It’s one of the few areas where component-level decisions directly influence system-level performance.

A Practical Next Step

For teams designing or optimizing liquid cooling systems, validating material compatibility early can prevent costly issues later in deployment.

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Final Thought

Material compatibility isn’t just about avoiding failure; it’s about enabling consistency as systems scale. As liquid cooling becomes the backbone of next-generation data centers, getting these details right upfront can make the difference between reactive maintenance and long-term reliability.