Any reason not to powdercoat aluminium? (Will I die content)

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  • Any reason not to powdercoat aluminium? (Will I die content)
  • Premier Icon igm
    Subscriber

    Got a frame that wants respraying, but the manufacturer says no powdercoating.

    Now it’s out of warranty anyway so that’s not a problem, but does anyone know why a manufacturer would recommend not powdercoating?
    Does it spontaneously decompose?

    thomthumb
    Member

    heating may effect heat treatment.

    heating may effect heat treatment.

    Doubt it. Aluminium frames are heat treated after welding to stress relieve and normailise – the heat used is much higher than that used for powder coating.

    There was a great (well, awful) before & after pic on mtbrider.com of an unfortunate bloke who had his Giant Reign powdercoated.

    The powdercoater used too high a temperature to bake it, which softened the tubing – when he rode the bike, the downtube stretched/deformed. The “after” pic showed the bike visibly lower/longer/slacker – and not in a good way.

    I_Ache
    Member

    I have done it and it turned out fine. Just go to somebody who has done aluminium before or even better bike frames. The place where I took mine did all the masking and prep work for me and seemed to charge no more than others were paying for theirs.

    Edit: Here you go before and after pictures.


    mtbtomo
    Member

    When I got mine done, the company that did it had done alu frames before and knew how to get the old paint stripped.

    Getting the old paint stripped was, as I understood it, where the damage could occur – not the actual powder coat process.

    Paint can be removed in a number of ways, and not all of them are suitable for thin walled aluminium.

    What frame is it?

    toys19
    Member

    I have been over this a good few times on here before, there are some very good reasons not to have your frame powder coated.

    here are some of the previous discussions

    http://singletrackworld.com/forum/topic/does-respraying-a-frame-weaken-it
    http://singletrackworld.com/forum/topic/powder-coating-my-heckler

    Premier Icon igm
    Subscriber

    Interesting reading Toys.

    Struggling to find a sprayer round here (they all want to powdercoat at 200C), but Bob Jackson Cycles in Leeds will enamel it for me and say their process goes to roughly 200 Fahrenheit – that sounds like it should be OK at around 100C.

    Any thoughts on that?

    Is it just me or do all re-powder coated frames look as though they’ve all been nicked.

    Premier Icon thisisnotaspoon
    Subscriber

    The coating bit is usualy fine, the problems are in the stripping, use the wrong media and a good aluminium* frame will be reduced to swiss cheese in seconds. IMO this is where most of the failures come from, the process removes too much material leaving the frame weak.

    Find a good powdercoater localy, there’s always one thats used to doing bike frames and can strip the old paint off and mask it properly.

    *what’s the bike made from? Carbon fibre is a big NO, aluminium is generaly fine if done correctly but it’s easier to exclude doing it from warenties than it is to argue who was responsible to for messing up, steel is easy as pretty much any blasting media will be softer than the frame.

    thisisnotaspoon – Member

    The coating bit is usualy fine

    Reading what that toys chap has posted on the threads linked above, I’m not so sure it’s “usually fine” – reads to me like temperatures routinely used for powdercoating could affect the strength of an Alu frame.

    I’d be wary of any heat treatment, on the face of it it looks like it could be fine but it might not, ally is a bit heat sensitive so why not just have it painted? My local car shop did my frame for 50 notes and it looked really good.

    toys19
    Member

    igm, 100c would be fine, but the important thing is ensuring the powder coaters only do it at 100c, do they have a thermal map of their oven? Can they control temps accurately, are operators aware that they should not leave the parts in the oven for too long. Engineering heat treatment is controlled accurately, I’m not in any way convinced that powder coating temps are controlled very well in your average powdercoaters.

    I know of aluminium part manufacturers who either carry out their powder coating in house or put close controls on their external contractors with regards to temps. Is the risk worth it? Just get a car body place to spray it.

    toys19
    Member

    Is it just me or do all re-powder coated frames look as though they’ve all been nicked.

    Well given my own distrust of after market powder coating I always avoid a powder coated 2nd hand frame anyway….

    Premier Icon thisisnotaspoon
    Subscriber

    Reading what that toys chap has posted on the threads linked above, I’m not so sure it’s “usually fine” – reads to me like temperatures routinely used for powdercoating could affect the strength of an Alu frame.

    Indeed, in the same way as doing 6ft drops would be ‘usualy fine’ if you can ride drops, if you can’t then it would probably result in a similar looking frame.

    I’m sure with a bit of googling you could turn up plenty of threads saying do or don’t do anything. But powdercoating seems to work for 99% (made up statistic, it’s probably more) of bikes. And the bulk of failures I’ve seen are allong the lines of “I took my frame to the local industrial fence post coating company and they treated it like a fence post”.

    plyphon
    Member

    sandblasting or using other abrasive media can reduce the thickness of aluminium which is why a number of manufactures say not to do it.

    renton
    Member

    I’m getting my 5 spot sent off next week to a company called fast line coatings who have done some frames before!!

    Fingers crossed it won’t come back looking like it’s stolen!!

    Will do a full write up on it when inget it back

    why do people think powdercoat is awesums

    paint = milk nice tasting and good for you
    powdercoat = powdered milk generally **** useless for anything

    compositepro- think you are mixing up powdercoat and poster paint there.

    compositepro- think you are mixing up powdercoat and poster paint there.

    poster paint has created some awesome childrens works of art

    Raising the temp of the aluminium can cause distortions in the frame as the residuals stresses which can never be fully relieved, and sometimes you don’t want them to be, will distort the frame. Also it depends upon the aluminium alloy they’ve used. Some age harden over many years but elevating the temp will affect the properties and you may end up with a frame more susceptible to fatigue cracking. I’d take the manufacturers advice.

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