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 Post subject: Bare magnesium?
PostPosted: Sun Aug 25, 2013 5:05 am 
Retro Guru
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Joined: Mon Mar 30, 2009 7:41 am
Posts: 1083
Location: Christchurch, New Zealand
So I've sanded the brace on my Judy SLs back so it's nice and shiny. I was fully intending on repainting it, but have actually grown to like the shiny look.
Can I leave it bare? Or will it disintegrate?


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 Post subject: Re: Bare magnesium?
PostPosted: Sun Aug 25, 2013 7:30 am 
Retro Guru
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Joined: Fri Sep 19, 2008 4:37 pm
Posts: 5198
Location: North West
I think the later ... :-(

I think I read somewhere that in the aircraft industry there is a spec that gives a maximum time from stripping to painting, I seem to remember it was quite short and if not achieved, the part was scrapped ...

Even if structural issues weren't to much of an issue, I think it will tarnish quite quickly ?

WD :D


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 Post subject: Re: Bare magnesium?
PostPosted: Sun Aug 25, 2013 7:43 am 
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Joined: Mon Mar 30, 2009 7:41 am
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Location: Christchurch, New Zealand
Ok I'll finish sanding tomorrow and paint straight away.
Gutted cause it looks quite good.


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 Post subject: Re: Bare magnesium?
PostPosted: Sun Aug 25, 2013 8:15 am 
Retro Guru

Joined: Sun Apr 25, 2010 10:07 pm
Posts: 1319
Stick a clear coat of lacquer over it,that may work.


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 Post subject: Re: Bare magnesium?
PostPosted: Sun Aug 25, 2013 9:10 am 
retrobike rider
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Joined: Fri Aug 08, 2008 2:36 pm
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Location: Yorkshire, England
They tarnish very quickly.

I'd always assumed the brace was Aluminium to make it stiffer.


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 Post subject: Re: Bare magnesium?
PostPosted: Sun Aug 25, 2013 9:53 am 
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Joined: Sat Jan 22, 2011 11:22 pm
Posts: 358
Location: London
Just how much magnesium did Rockshox use in their fork alloys?

The alloy itself will be a determining factor here. Pure magnesium? Forget it, you'll never get a proper shine, and it'll oxidise before your very eyes. But magnesium alloys? You have a decent chance there.

Classic car buffs and motorcycle enthusiasts have been polishing up magnesium alloy parts for decades, with some success. Some hold a nice shine for ages, some don't. Lots of magnesium in the mix tends to be more gold in colour than aluminium, but the shine only lasts a few days before tarnishing if its not protected.

Clear coat lacquer is on option to protect the shine, but you'll probably have better results and a longer lasting shine with more modern liquid polymer sealants used on alloy wheels and paint finishes by car detailers. Something like this stuff from G-Techniq;

http://www.cleanyourcar.co.uk/wheels-an ... d_878.html


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 Post subject: Re: Bare magnesium?
PostPosted: Sun Aug 25, 2013 10:59 am 
King of the Skip Monkeys
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Joined: Wed Nov 07, 2007 4:34 pm
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Location: Moomin Valley
Polished Rock Shox forks last about a day in UK damp. Clear lacquer peels off very quickly as its unable to bond with the alloy still oxidizing underneath.


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 Post subject: Re: Bare magnesium?
PostPosted: Sun Aug 25, 2013 12:27 pm 
BoTM Winner / Gold Trader
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Joined: Fri Feb 26, 2010 12:36 am
Posts: 4715
Location: Burlington, ON Canada
WD Pro wrote:
I think I read somewhere that in the aircraft industry there is a spec that gives a maximum time from stripping to painting, I seem to remember it was quite short and if not achieved, the part was scrapped ...


I have a piece of billet mag given to me by a friend in the aerospace manufacturing industry (still haven't figured out what to make with it). The material was scrapped because someone touched it with their bare hands. Those satellite guys are serious. Then again, with the cost of a service call to replace a part, I can see why they're so anal.


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 Post subject: Re: Bare magnesium?
PostPosted: Sun Aug 25, 2013 12:41 pm 
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Joined: Sun Dec 18, 2011 7:43 pm
Posts: 771
Location: Netherlands
I've used to work for the dutch Rockshox importer and we've seen forks coming in from guys riding mostly on the beach. They had big holes even with the paint... :facepalm:


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 Post subject: Re: Bare magnesium?
PostPosted: Mon Aug 26, 2013 9:58 am 
Old School Grand Master
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Joined: Sun Sep 05, 2010 1:10 am
Posts: 4756
Location: Heathfield, East Sussex
A few useful pointers here...

http://www.englishcustompolishing.com/u ... inum1.html


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