[s-cars] Thermal properties of anodizing Aluminum

[Michael Bess]

FWIW, just remember that anodizing effectively turns the surface to aluminum
oxide, a ceramic with lower intrinsic thermal conductivity in comparison to
aluminum (which has a thermal conductivity on the order of 120-160
BTU/hr/ft^2 depending upon alloy & temperature).  In bulk form I would
estimate the thermal conductivity to be no more than 10% that of aluminum.
However, at the thin coatings we are talking about (.1 to 1.0 mils) the
effect would probably not be as large.  Without going into transport
equations, and realizing that any interface creates a thermal barrier, the
effect is there, but to what extent?  Also remember that aluminum will
naturally oxidize and create a similar thermal barrier.


Mike Bess
'95 S6


-----Original Message-----
From: s-car-list-admin at audifans.com [mailto:s-car-list-admin at audifans.com]
On Behalf Of mlp qwest
Sent: Wednesday, February 12, 2003 1:11 PM
To: s-car-list at audifans.com
Subject: [s-cars] Thermal properties of anodizing Aluminum

Anyone on the list have any particular knowledge or expertise on the thermal
effects of anodizing aluminum?

I gather there are at least three (3) major types or subcategories
anodizing, sometimes described or referred to as:

1.	Type 1 - "Chromic Acid" ~> usually leaves very thin deposit

2.	Type 2 - "Sulfuric Acid" ~>  ditto

3.	Type III aka "Hard Coating" ~> a much thicker process, which can be
done
in a way to add  very different characteristics to aluminum.  Type III
anodizing can, and is used to significantly inhibit aluminums otherwise high
thermal heat exchange capabilities, as for example in coating aluminum
pistons to reject heat etc.

Anyone know how processes 1 or 2 affect aluminums heat transfer
capabilities?
'
I'd like to know what, if any kinds of anodizing are done to ENHANCE heat
transfer either by conductivity, or for convection transfer purposes.

Thanks
Mikee "Wondering if there could be a Purple Anodized Radiator in some one's
future" P.


_______________________________________________
S-CAR-List mailing list
S-CAR-List at audifans.com
http://www.audifans.com/mailman/listinfo/s-car-list