Harry Phinney
You really want to hear from the aluminum frame or tubing manufacturer.
This is not a black-and-white, OK-or-not question. Many aluminum frames
are built with 6061 alloy aluminum, and are fully heat treated after
welding. The last portion of the heat treatment is termed "artificial
aging", and for 6061 is typically performed at temperatures around 300 F
to 400 F for specific periods of time that are on the order of one to
several hours. For any given temperature within the range there is an
optimum aging duration past which the metal's strength begins decrease
rather than increase. Going past this optimal point, either via too high
a temperature or too long a duration or some combination, is termed
"over aging". The peaks in these strength vs aging curves are not
terribly sharp - i.e. the strength losses for a _little_ over aging are
not huge. The bad news is that powder coat is generally cured at
temperatures in the upper range of the age hardening temperatures
(around 400 F / 200 C), and 20 minutes (a typical powder curing time) at
400 F can significantly reduce the strength of a previously optimally
hardened 6061 frame.
Other frames are made from 7005 alloy aluminum, and the proper post-weld
heat treatment consists of artificial aging at temperatures around 200 F
to 320 F for (depending on temperature) between 4 and 6 hours. I do not
know what affect 20 minutes at 400 F would have on a 7005 frame.
If you are going to get an Al frame powder coated then at least have the
coater use the lowest temperature and shortest cure time as is practical.
Harry Phinney
On 07/21/2015 06:58 PM, via OBRA wrote:
> It would be nice if someone is or knows a professional powder coater
> and would be willing to give us the information from that
> perspective. I had an aluminum frame powder coated and never saw any
> signs of a problem. I ended up selling the bike and if it does break
> and cause physical damage that would be bad! So, somebody who is or
> knows please give us more info. Powder coat is amazingly tough. I
> personally do not believe it is that much of a threat to alum. but
> only have the fact that many alum. products ARE finished with powder
> coat to base my belief.
> ron