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PostPosted: Mon Sep 02, 2013 12:36 pm 
Newbie

Joined: Wed Sep 12, 2012 8:08 am
Posts: 8
Hi

Hoping someone can help with alu frame restoration advice.

Recently took a 7005 alu MTB frame to a powder coaters in Eastleigh. The frame was originally finished with a translucent paint over a silver/chrome effect base. Once stripped it appears the aluminium had oxidised under the silver base coat in one or two places. In doing so it must have lifted the paint slightly as it wasn’t visible through the original paint.

I expected some oxidisation as there was an amount elsewhere so my expectation was the raised oxidisation could just be sanded down and then powder coated.

Unfortunately the powder coaters were unable/unwilling to do this and instead layered additional powder coat over the frame in an attempt to hide the oxidisation as best as possible. As a result the powder coat has run in a few places and isn’t that great but on the plus side it’s bloody thick! At the time though not 100% happy with the result it would do for what I wanted the bike for.

However the more I look at it the less I’m happy with it and if I build it up I know it’s going to constantly annoy me.

So am I right in my assumption that if stripped again I can just sand that raised oxidisation down so it’s smooth and level with the tubing and get powder coated again? Or am I best just sticking with the result I have as it’s the best I can expect?

Cheers


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PostPosted: Mon Sep 02, 2013 1:02 pm 
MacRetro rider
MacRetro rider

Joined: Fri Feb 09, 2007 4:16 pm
Posts: 8658
If its not going to cost you extra then I'd restrip, smooth and recoat. If it is going to cost, speaking as a Scotsman, I'd learn to live with it :roll:


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PostPosted: Mon Sep 02, 2013 2:21 pm 
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Joined: Wed Sep 12, 2012 8:08 am
Posts: 8
:) Heh I don't mind the extra cost to strip it back to bare metal and start again as the annoyance I'd get looking at it each time would be worse.

I guess my question was more can I smooth it right down? I assumed there would be nothing wrong with smoothing the oxidisation down but given the powder coaters couldn't smooth it themselves it makes me question whether it can be done without weakening the frame.

I assume they know what they are doing but can't help but feel maybe they don't.


Last edited by Agent Orange on Mon Sep 02, 2013 3:17 pm, edited 1 time in total.

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PostPosted: Mon Sep 02, 2013 3:03 pm 
Retro Guru
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Joined: Sun Mar 14, 2010 2:33 am
Posts: 2923
Location: daaan saaaf
You could try to smooth out the runs with some very fine wet & dry, followed by either some T-Cut or metal polish, something like Brasso. Use the wet & dry with a sanding block or wrapped around a small piece of wood, so that you keep the wet & dry flat; this is important as you only want to smooth off the raised run and not the surrounding area. Once you've sanded use the metal polish to buff up the area to a shine again. You might not get it absolutely perfect, but you should be able to reduce the visibility of the runs significantly.

http://www.youtube.com/watch?v=uB02f6xvajQ


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PostPosted: Mon Sep 02, 2013 8:51 pm 
retrobike rider
retrobike rider

Joined: Thu Apr 17, 2008 1:24 am
Posts: 7563
Location: Manchester
Do you have a picture?
Chances are if it's raised then its also very pitted, the oxide formation has come from somewhere. It might end up looking worse.


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PostPosted: Mon Sep 02, 2013 9:36 pm 
Newbie

Joined: Wed Sep 12, 2012 8:08 am
Posts: 8
Not easy to see on the photos but try these. We suspect the original oxidisation came from a scratch in the down tube that cut through the original paint. Possibly because the frame wasn't absolutely clean when original painted at the factory the moisture managed to get under the silver base coat.

Surely the powder coaters could have just sanded this down and smoothed it to the down tube?

Image
Image


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PostPosted: Mon Sep 02, 2013 10:10 pm 
Retro Guru
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Joined: Sun Jun 05, 2011 9:41 pm
Posts: 365
Location: WEST MIDLANDS
they may have tried to remove it but aluminum oxide is one off the hardest materials around thats why they use it to make sanding papers and disks (stange but true)
leave it as it is and ride your bike


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PostPosted: Wed Sep 04, 2013 1:42 pm 
Newbie

Joined: Wed Sep 12, 2012 8:08 am
Posts: 8
Makes a bit of sense now thanks.

They did try to remove it but were cautious of blasting it too much. I wish they'd have made my options clearer as in hindsight it looks like I could have take the frame after they'd stripped it and with a lot of elbow grease smoothed it down manually.

Still it probably isn't worth a complete strip and re-coat for a mark that I hope I'll get used to and ignore.


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PostPosted: Wed Sep 04, 2013 9:35 pm 
retrobike rider
retrobike rider
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Joined: Wed Mar 03, 2010 11:59 am
Posts: 4437
Location: Near Southampton
Just out of interest I am in Chandlers Ford....what powder coaters did you use?


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PostPosted: Wed Sep 04, 2013 9:42 pm 
Newbie

Joined: Wed Sep 12, 2012 8:08 am
Posts: 8
Solent Powder Finishers. They have a good reputation but I'm so/so based on the work they did for me. Put it this way I wouldn't use them again and I have had far better results from powder coating in the past from other companies. Unfortunately those companies no longer exist.

http://www.solentpowderfinishers.co.uk/domestic/


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