Building resilient cooling systems: avoiding the pitfalls of CAB in aluminium heat exchangers

What is Controlled Atmosphere Brazing (CAB)?

Modern heat exchangers, such as radiators and cold plates, are predominantly manufactured using aluminium alloys through a process called Controlled Atmosphere Brazing (CAB). This technique involves heating aluminium components in a nitrogen-rich, oxygen-free environment to bond them together. A non-corrosive flux is applied to remove surface oxides and promote bonding between components. The flux displaces the oxide layer, allowing the filler metal to flow and preventing oxidation during brazing.

CAB is widely used in automotive and HVAC heat exchangers and is increasingly relevant in data center liquid cooling systems where aluminium is used.

How flux residue in CAB-brazed heat exchangers can compromise coolant performance

Residual flux remaining on aluminium surfaces can interact with some coolant formulations.  Studies have shown that flux residue can cause aluminium corrosion.

This interaction may result in:

•  Ammonia formation

•  Increase in pH value

•  Rapid depletion of inorganic corrosion inhibitors

•  Deposit formation

•  Blockage of coolant passages

•  Heat exchanger failure

These risks are greatest in newer, more complex heat exchanger designs, where higher residual flux loads are present relative to the coolant volume, posing a particular concern for data centers that demand long-term cooling system durability and reliability.

Why AI and high-power computing demand better coolant compatibility

As computing systems evolve, the thermal demands placed on cooling systems are intensifying. AI workloads generate significantly higher heat densities, requiring more efficient and stable cooling solutions. In such environments, even minor inefficiencies or chemical instabilities caused by flux residue can lead to rapid thermal degradation, reduced performance, or hardware failure.

This makes flux management and coolant compatibility a critical consideration in next generation cooling architectures.

How ZITREC EC coolants protect aluminium systems against flux residue and corrosion

ZITREC^® EC direct-to-chip coolants are formulated with Organic Additive Technology (OAT), which enhances compatibility with aluminium and flux-treated surfaces. ZITREC^® EC coolants inhibit corrosion, prevent gel formation, and passivate metal surfaces to ensure consistent heat transfer.

A key innovation of the ZITREC^® EC formulation is the flux compensation package. Additives in ZITREC^® EC neutralize residual flux within the cooling system. This technology optimizes thermal performance and extends the lifespan of your systems, especially under the demanding conditions of AI and high-power computing.

Why ZITREC EC 30 is engineered for data center and high-power liquid cooling

ZITREC^® EC 30 is a premium ethylene glycol-based heat transfer fluid tailored for data centers and electronic applications. It combines OAT technology with a flux compensation package, offering robust protection against corrosion and chemical instability in aluminium-based systems

Key product highlights are:

•  Flux stabilization for CAB-manufactured surfaces

•  Aluminium protection at elevated temperatures

•  Excellent compatibility with common elastomers and thermoplastics 

•  Biostatic matrix inhibiting growth of micro-organisms

•  Leak detection package available

•  Available in variants using bio-based base fluid to reduce carbon footprint