The effect of powdercoating heat treated aluminium.

[Rampage]

This is something I've never seen mentioned on here but I have seen it mentioned on metal finishing forums before. I've never had anything definate about it just 'internet rumours'.

This is a Ministry of Defence document:

It's obviously a bit vague but it says it happens.

 

[phill77]

I've seen it mentioned a few times on bike forums that you need to be careful with certain grades of aluminium when powder coating. I gather it ages the material further, potentially weakening it. Some people claim that some manufacturers use the powder coating process to perform the heat treating process.

I'll be spraying my 6061-T6 frame anyway!

 

[cornholio's RC200]

Strange that my first Proflex cracked about 2 months after powder coating. Mind you, hitting the Ford Focus might have had a bit do do with it as well...

 

[REKIBorter]

I have been told on good authority that the temperatures used in powdercoating (180C) are not high enough to affect heat treated aluminium.

 

[Tazio]

I have been told on good authority that the temperatures used in powdercoating (180C) are not high enough to affect heat treated aluminium.

What I've been told is that it isn't a huge problem but not something you would want to do more than once or twice.

But then again I've been told by a powdercoater it isn't a problem in any way.

 

[phill77]

It depends on the baking temperature and time.

Temperatures over 180 deg C or for a duration of over 30 minutes will start to affect the strength of 6061-T6. Obviously other alloys may be different.

I know some powders need heating at over 200 degC which would start to make me worry.

 

[NeilM]

So what is the best method for aluminium?

I ask, as I'm just about to have an aluminium frame painted / powder coated.

I was thinking about stove enamel, but perhaps I'd be safer with two pack, as I believe the frame has already been powder coated once.

 

[Raymond_mole]

These ally frames are subjected to higher temperatures while going through the normalising process.
The T6 indicates that the material has been taken to a set temperature 6 times. Normally over 200 degrees
This helps welded components mate and avoids weak areas that have been subjected to stress such as bending machining or welding.

Anodising and getting items reanodised is far more damaging, as the pickling process removes material.

Saying that it woulnt stop me doing either to make it look nice

 

[integerspin]

These ally frames are subjected to higher temperatures while going through the normalising process.
The T6 indicates that the material has been taken to a set temperature 6 times. Normally over 200 degrees
This helps welded components mate and avoids weak areas that have been subjected to stress such as bending machining or welding.

Anodising and getting items reanodised is far more damaging, as the pickling process removes material.

Saying that it woulnt stop me doing either to make it look nice

Never heard the 6 times bit.

I have castings heat treated, to TF which is the same as US T6.
For the alloy I have cast the heat treatment to TF is something like:
Heat for 12 hours at 525ºC and quench in hot water, that is solution treatment. Then precipitation treat, 12 hours at 155ºC.

I had to weld a casting up. I mentioned it at the foundry and they said above 130º and the heat treatment is effected.

 

[merckx]

bitd i had my alloy bike powdercoated.

not long thereafter, it developed stress cracks everywhere and failed.

i for one, would never powdercoat an alloy frame again. and if i was getting it sprayed, i would be careful about what temp the guys might "bake" it if they did so.