Bare Aluminum vs. Anodized Heat Sink

Written by jacob andrew
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Bare Aluminum vs. Anodized Heat Sink
A "finned" heat sink has more surface area for dissipating heat. (cpu radiator image by saied shahinkiya from

As computer central processing units become more powerful, the heat sink has played an increasing role. Heat sinks, which are made of various metals, help disperse heat from CPUs, which could be irreparably damaged by overheating.

Types of Aluminum

"Bare" aluminium is something of a misnomer, as few heat sinks are made of pure aluminium. Aluminium alloys are used to create the finned designs that help disperse heat; however, the most efficient aluminium alloy is too soft to be machined. Bare aluminium is often an alloy called Aluminum 6063 or 6061.

Forced Air vs. Natural Convection

Anodised heat sinks are generally recommended where only natural convection is used. Convection is the movement of heat through liquids or gas, such as when warm air rises. This normally happens as varying air masses meet (e.g., air around a heat sink meets the cooler air of a computer case).

In a forced-air convection system, a fan moves hot air off of the heat sink. Although natural convection application benefits greatly from anodising, forced-air system see a benefit of only 4 per cent to 8 per cent.

Bare Aluminum vs. Anodized Heat Sink
Heat sinks designed for use with fans are generally not anodised. (heat sink image by Sonar from


Because the objective of a heat sink is to release thermal energy as quickly as possible, "bare" aluminium cannot be painted for fear of affecting these thermal properties. Anodization is a process that merely oxidises the outer layer of a metal, preserving its conductive properties. The aluminum oxide coat can be dyed a wide selection of colours. Anodised heat sinks can make an electronic device appear more appealing than the dull, silvery finish of aluminium.

Bare Aluminum vs. Anodized Heat Sink
Colour anodising doesn't affect a heat sink's thermal properties. (cooler image by TEA from

Corrosion resistance

Anodising ensures that the aluminium is safe from corrosion, although this isn't usually needed in a computer. Anodised heat sinks are preferable where corrosion is possible.

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