A bare aluminum heat sink conducts heat well but sheds very little of it as radiation. Its shiny surface reflects instead of emits. A high emissivity coating for aluminum and copper heat sinks adds a second cooling path, radiation, on top of the convection the fins already provide.
Q: Why Coat an Aluminum or Copper Heat Sink for Emissivity?
A: To Add Radiative Cooling That Bare Metal Surfaces Barely Provide
Every surface loses heat in two ways: to the surrounding air by convection, and as infrared radiation. How well a surface radiates depends on its emissivity. Bright, bare aluminum and copper are poor radiators, so almost all of their cooling comes from airflow.
A dark, high-emissivity ceramic coating changes that balance. It lets the same heat sink, or the outer wall of an electrical enclosure, radiate far more heat without a larger fan or more fin area. The gain is most useful where airflow is limited: sealed enclosures, natural-convection heat sinks and equipment in still air.
Incure’s grade for this job is Epo-Weld™ HECC-636, a silicone-ceramic emissivity coating developed specifically for non-ferrous metals such as aluminum and copper, rated by Incure for service up to 1,100°F.
Why HECC-636 Differs From the Rest of the HECC Line
The other Epo-Weld™ HECC grades are built for furnaces, kilns and steel process equipment running far hotter. HECC-636 is the line’s lower-temperature, non-ferrous specialist, and two details explain why.
A flexible silicone binder. Aluminum and copper expand considerably more with heat than a rigid ceramic coating does. Incure’s catalog notes that HECC-636’s flexible silicone binder and ceramic fillers resist cracking and delamination caused by that thermal expansion mismatch. A rigid furnace coating on aluminum is far more likely to craze or flake over repeated heating and cooling.
A thin, low-viscosity film. HECC-636 lists a viscosity of 500–750 cps, the lowest in the HECC line (the furnace grades run 1,000–4,000 cps). A thin coating suits fin arrays, where a thick, heavy layer could fill fin gaps, restrict airflow and insulate rather than help.
Like the other grades in the line, HECC-636 lists 1,100 PSI flexural strength, 300 PSI tensile shear strength and a cure of 1 hour at 200°F.
Where It Is Used
Incure recommends HECC-636 for heat sinks and electrical enclosures. Typical candidates include:
- Passive and natural-convection heat sinks on power electronics, LED drivers and industrial controls.
- Sealed electrical enclosures whose outer walls must reject internal heat without vents.
- Copper or aluminum heat spreaders and housings in still-air or outdoor locations.
Incure’s catalog also lists resistance to moisture, chemicals and weathering, which matters for enclosures mounted outdoors or in washdown areas.
Email Us with your heat sink or enclosure material, operating temperature and airflow conditions to confirm whether HECC-636 fits.
Applying the Coating to Fins and Enclosures
- Degrease thoroughly. Machining oils and fingerprints on aluminum and copper block adhesion and are where peeling starts.
- Coat evenly and thinly. Aim to cover fin surfaces without bridging the gaps between fins. A sprayed or brushed thin film keeps the airflow path open.
- Cure fully before service. Complete the 1 hour at 200°F cure before the part goes into use, so the binder is set before it sees operating heat.
- Mind the interfaces. Keep coating off contact faces where the heat sink mounts to a component. Those joints rely on a thin, controlled thermal interface, covered in Incure’s guide to validating a thermally conductive epoxy bond line for heat sinks.
Measuring the Result Correctly
The simplest proof is a before-and-after test: run the same heat sink at the same load and airflow, uncoated and then coated, and compare its steady-state temperature. How you measure matters.
Use a contact thermocouple, not a handheld infrared thermometer. Infrared tools read temperature from emitted radiation, and they assume a fairly high emissivity. On bright, bare aluminum or copper, an infrared reading can come out well below the true temperature, because the shiny surface emits so little. After coating, the same tool reads much closer to the truth. Comparing infrared readings before and after can therefore exaggerate, or hide, the real improvement.
Record ambient temperature with each run too. Both convection and radiation depend on the gap between the part and its surroundings, so readings taken on a cool morning and a hot afternoon are not directly comparable.
Choosing the Right HECC Grade
If the part is aluminum or copper and runs below 1,100°F, HECC-636 is the starting point. Steel, refractory and ceramic-fiber surfaces in furnaces need one of the higher-temperature HECC grades instead, compared in Incure’s overview of Epo-Weld™ HECC coatings by substrate and service temperature. For background on why emissivity drives radiant heat transfer, see what a high-emissive ceramic coating is and why emissivity matters.
Final Thoughts
A high emissivity coating for aluminum and copper heat sinks adds radiative cooling where bare metal provides almost none. Incure’s Epo-Weld™ HECC-636 does it with a flexible silicone-ceramic film that tolerates non-ferrous expansion and stays thin enough to keep fins clear. Contact Our Team to qualify it for your heat sinks or enclosures.
Visit www.incurelab.com for more information.