Which heatsink surface treatment to choose?

Do you know that a surface treatment of an aluminium enclosure has a significant influence on its efficiency depending on conditions in which it´s used?
This is an archive article published 09/28/2017. Some information may no longer be up to date and in line with the current state. Please contact us in case of interest.

Abbreviations like “Natural Al“, “Natural elox“ and “Black elox“ marking various surface treatments of components made of aluminium alloys are probably familiar to you. However, is it only a “cosmetic” or aesthetic matter or is it a parameter, which has to be considered also from technical point of view?

The answer is simple – it is a key parameter for majority of applications. Surface treatment has a significant influence mainly on these three features:

1) Abrasion resistance – surface of common aluminium alloys (whether enclosures or heatsinks) has a typical “aluminium” colour (natural Al). After wiping with, for example a bare hand, usually you´ll find a dark mark on your hand. It is in fact a micro-layer of aluminium (and its oxides), which you´ve just removed from its surface. Aluminium is a relatively soft metal and thus it features low abrasion resistance (in a basic – untreated status). Much better from this point of view are electrolytically oxidized (anodized/elox) surfaces, where an oxide layer is much thicker than it would arise at common conditions. Deposited Al2O3 is a very hard material (Corundum) and therefore, this layer is very resistant to abrasion. If you scratch the anodized surface, it's a bit like "pulling" this layer of relatively soft aluminium with some hard and sharp object.

2) Chemical resistance – as we know, aluminium alloys can be categorized within “corrosion-resistant” materials - at common conditions and in a clean and dry environment. Aluminium itself, however, easily reacts with various acids and alkali and many times even a fingerprint is enough to be “baked in” after some time (if not removed on time). Even in this respect, an anodized surface is much more resistant and elox is effectively protecting aluminium surface even in harsh conditions. That´s also a reason why aluminium components intended for outdoor use are being always anodized (if an aesthetic aspect is important).
3) Cooling efficiency – at the end, perhaps the most important parameter. Untreated natural aluminium with a glossy surface features extremely low emissivity – simply said, a parameter defining heat radiation ability of a given surface. An emissivity of a vast majority of materials is approximately 0,95. Despite that, a glossy aluminium has emissivity of approximately only 0,05 (!), meaning that if a glossy heatsink gave off heat only by radiation, its efficiency would be dramatically low. Fortunately, convection (heat flow) also contributes to a heat transfer and it depends mainly on the size of the surface of the heatsink and the way the air heats up the radiator ribs. Even though it may not seem logic, even the bright natural anodized heatsink surface has significantly higher emissivity than a natural Al surface – approx. above 0,80. That´s why even seemingly similar surfaces (non-anodized vs. natural anodized) feature significantly different emissivity.
Influence of emissivity can be illustrated in two examples:
a) small glossy heatsink (non-anodized) for a transistor in TO220 package in a small closed enclosure (minimum air movement) will transfer a big portion of heat by radiation. That´s why in this case it would be very suitable to better use black-anodized surface.

b) heatsink directly fanned by fan gives off a vast heat majority by convection to the air flowing around, that´s why no surface treatment is necessary (as for heatsink efficiency).

If you also belong to designers, who control temperature by an infrared thermometer or camera, don´t forget to set the emissivity before measuring - according to the heatsink surface. Otherwise you might easily measure very misleading values.

Heatsinks with all three common surface treatments can be found in our iffer. Heatsinks from company Fischer elektronik are supplied with a natural- or black anodized surface, according to abbreviation in their name (SA = black anodized, ME = natural anodized, AL = raw degreased aluminium).
In case of interest in any heatsinks, please contact us at sales@soselectronic.com

Do not miss these articles

Do you like our articles? Do not miss any of them! You do not have to worry about anything, we will arrange delivery to you.

Additional products


SK 64 37,5 SA FISCHER ELEKTRONIK  
SK 64 37,5 SA

Heatsink AL black anodized 70x25x37,5mm 4,1K/W

Standard Heatsinks

Ord. No.: 8017
Manufacturer: FISCHER ELEKTRONIK
in stock 6 pcs
1 pcs+
10 pcs+
30 pcs+
120 pcs+
3,49 €
2,95 €
2,83 €
2,58 €
  • ADD TO CART
  • Get Quote
  • Add to favorites
  • Add to watchdog
  • Add item to compare

ZH-9099/1000 GAMA ALUMINIUM  
ZH-9099/1000

Heatsink AL anodized L=1000mm for LED Strip

Standard Heatsinks

Ord. No.: 123801
Manufacturer: GAMA ALUMINIUM
  • ADD TO CART
  • Get Quote
  • Add to favorites
  • Add to watchdog
  • Add item to compare
Get Quote

A59/40AL GAMA ALUMINIUM  
A59/40AL

Heatsink AL standard L=40mm 39x59

Standard Heatsinks

Ord. No.: 65651
Manufacturer: GAMA ALUMINIUM
  • ADD TO CART
  • Get Quote
  • Add to favorites
  • Add to watchdog
  • Add item to compare
Get Quote

D 01 A (FK301A) VARIOUS  
D 01 A (FK301A)

Heatsink standard TO-220 13,3x19,1x12,7mm

Standard Heatsinks

Ord. No.: 6417
Manufacturer: VARIOUS
in stock 270 pcs
10 pcs+
20 pcs+
50 pcs+
500 pcs+
1500 pcs+
0,2720 €
0,2630 €
0,2410 €
0,2120 €
0,2040 €
  • ADD TO CART
  • Get Quote
  • Add to favorites
  • Add to watchdog
  • Add item to compare

K112/60AL GAMA ALUMINIUM  
K112/60AL

Heatsink AL standard L=60mm 111,5x67,5

Standard Heatsinks

Ord. No.: 65749
Manufacturer: GAMA ALUMINIUM
in stock 5 pcs
1 pcs+
2 pcs+
10 pcs+
40 pcs+
9,82 €
9,13 €
8,38 €
7,66 €
  • ADD TO CART
  • Get Quote
  • Add to favorites
  • Add to watchdog
  • Add item to compare

HY 25346 (KE82/40AL) GAMA ALUMINIUM  
HY 25346 (KE82/40AL)

Heatsink AL standard L=40mm 82x32

Standard Heatsinks

Ord. No.: 65675
Manufacturer: GAMA ALUMINIUM
in stock 21 pcs
1 pcs+
20 pcs+
40 pcs+
160 pcs+
2,53 €
2,07 €
2,02 €
1,89 €
  • ADD TO CART
  • Get Quote
  • Add to favorites
  • Add to watchdog
  • Add item to compare

SK 104 25,4 LS FISCHER ELEKTRONIK  
SK 104 25,4 LS

Heatsink AL black anodized 34,9x12,7x25,4mm 14K/W

Standard Heatsinks

Ord. No.: 10009
Manufacturer: FISCHER ELEKTRONIK
in stock 36 pcs
2 pcs+
4 pcs+
10 pcs+
70 pcs+
290 pcs+
1,45 €
1,40 €
1,28 €
1,16 €
1,06 €
  • ADD TO CART
  • Get Quote
  • Add to favorites
  • Add to watchdog
  • Add item to compare

SK 68 50 SA FISCHER ELEKTRONIK  
SK 68 50 SA

Heatsink AL black anodized 46x33x50mm 5K/W

Standard Heatsinks

Ord. No.: 8019
Manufacturer: FISCHER ELEKTRONIK
in stock 1 pcs
(04/12/2024: 5 pcs)
1 pcs+
5 pcs+
20 pcs+
100 pcs+
4,01 €
3,57 €
3,30 €
3,07 €
  • ADD TO CART
  • Get Quote
  • Add to favorites
  • Add to watchdog
  • Add item to compare

T88/40AL GAMA ALUMINIUM  
T88/40AL

Heatsink AL standard L=40mm 88x35

Standard Heatsinks

Ord. No.: 65688
Manufacturer: GAMA ALUMINIUM
in stock 1 pcs
1 pcs+
20 pcs+
40 pcs+
160 pcs+
2,55 €
2,09 €
2,04 €
1,91 €
  • ADD TO CART
  • Get Quote
  • Add to favorites
  • Add to watchdog
  • Add item to compare
Do you agree with cookies being stored?
Welcome to the SOS electronic website. Before you enter our online world, we would like to ask you to allow us to store cookies on your browser. Your consent will help us view the site without error, measure its performance, and track additional statistics. Apart from that, we can bring you an offer of our products and services, literally tailor-made. We also provide cookies to third parties. However, you are definitely safe with us.
The proper operation of the website
More stable technical control
Better marketing offer

More about cookies
More about personal data processing

Necessary Only selected Accept all cookies