What is anodization?

"Black, slim and surprisingly powerful for a passive CPU cooler: The undoubtedly most striking feature of the new ARCTIC Alpine Passive coolers is the black heat sink. Unlike the thermal coating of the Freezer 33 eSports family, however, this is not a thermal coating, but the color is created by anodization.

But what is this and how does it work? Anodic oxidation is a special process in which the object to be treated is placed in a conductive liquid and this liquid is connected to a voltage source. The object to be treated is one of the poles, the opposite pole is usually another, non-rusting metal such as lead, aluminum or stainless steel.

To color the Alpine Passive, the conductive liquid is accompanied by black dye, which accumulates in the oxidation process in the pores of the aluminum. The advantage: it forms an extremely dense, micro-porous and dust-free barrier layer, which additionally functions as an electric insulator.

For the end-user, this complex process brings one major advantage: The black anodization ensures improved heat dissipation in fanless operation. Due to the changed surface structure, micro turbulences occur during heat radiation which lead to a higher cooling capacity. Compared to other passive coolers of the same size, but without anodization, the ARCTIC Alpine Passive is doing very well: Internal tests showed an improved cooling performance of up to 3°C."

Source: ARCTIC