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Cabinet and Chassis Restoration and Refinishing For help with cabinet or chassis restoration (non-electrical), please leave a message here. |
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9th Sep 2017, 3:53 pm | #1 |
Pentode
Join Date: Aug 2005
Location: Shrewsbury, Shropshire, UK.
Posts: 149
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Re-anodising heatsinks?
I found out the hard way today that putting anodised aluminium heatsinks in the dishwasher to clean them is a very bad idea. They're now a sort of streaky grey with black areas where the devices were mounted. "Mortified" is the word.
Is it possible to get heatsinks re-anodised? |
9th Sep 2017, 4:33 pm | #2 |
Dekatron
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 7,081
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Re: Re-anodising heatsinks?
The alkaline solution of dishwasher tablets attacks aluminium, as you've found out!
Depending on how bad the surface is, you may be lucky. Take a few photos and email South West Metal Finishers. No connection apart from a satisfied customer in the day job! |
9th Sep 2017, 5:05 pm | #3 |
Pentode
Join Date: Aug 2005
Location: Shrewsbury, Shropshire, UK.
Posts: 149
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Re: Re-anodising heatsinks?
Oh well. I learned a lesson from that mistake. The surface feels very smooth so hopefully something can be done; I've e-mailed as you suggest and will see what transpires. Fingers crossed...
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9th Sep 2017, 7:11 pm | #4 |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,982
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Re: Re-anodising heatsinks?
Black anodising is essentially cosmetic for a heatsink that is not running stinking hot.
The majority of heat transport from a heatsink is via convection, not radiation, for typical heat rise of say 40C. In that case the difference between a black anodised heatsink and a shiny aluminium one is negligible that for typical heat rise. Rather than pay for a small quantity to be stripped to bare metal and re-anodised, I'd be tempted to spray paint them black. |
9th Sep 2017, 7:19 pm | #5 |
Heptode
Join Date: Apr 2016
Location: Cheltenham, Gloucestershire, UK.
Posts: 875
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Re: Re-anodising heatsinks?
Per Craig: If you use VHT [AKA Very High Temperature] spray paint there is no chance that this will lift or bubble .... this stuff is used by car restorers etc. on exhaust manifolds. (It goes under then name of VHT / 'Firecote' etc. Retailed by CarPlan - made by Tetrosyl Ltd. Bury, Lancs. BL9 6RE. Tel. 0161 764 5981.)
They'll be fine ..............
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Red to red, black to black. Throw the switch and stand well back! |
9th Sep 2017, 7:54 pm | #6 |
Pentode
Join Date: Aug 2005
Location: Shrewsbury, Shropshire, UK.
Posts: 149
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Re: Re-anodising heatsinks?
That's interesting -- thank you. Does this type of paint work well on aluminium? I seem to recall reading horror stories about needing etch primer or exotic surface preparation to make paint adhere properly.
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9th Sep 2017, 8:33 pm | #7 |
Dekatron
Join Date: Apr 2009
Location: Oxfordshire, UK.
Posts: 4,934
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Re: Re-anodising heatsinks?
For an outlay of 15 shillings, anodising can be done in the average home...according to PW in 1962 (see attached)!
I wonder how big your heatsink(s) are? PM me if you consider any "homebrew" option. As for dish washers, I have put the odd item of agricultural engineering in them, but never any item of radio/electronics. B
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Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch. |
9th Sep 2017, 9:24 pm | #8 |
Dekatron
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 7,081
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Re: Re-anodising heatsinks?
Worth trying for some fun!
I believe after dyeing, commercial anodising features a further electrolytic operation which hardens the oxide coating and makes it more dense. This is missing from the PW article. But I may be wrong on this. Hopefully someone will correct me! Look forward to what South West Meatl Finishers come up with. If time is not of the essence, they may offer to wait till a big batch of something arises, and put it in at the same time for a nominal sum. |
9th Sep 2017, 10:32 pm | #9 | |
Pentode
Join Date: Aug 2005
Location: Shrewsbury, Shropshire, UK.
Posts: 149
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Re: Re-anodising heatsinks?
Quote:
Not sure the homebrew option would go down very well with Madam or the elf 'n' safety people nowadays.... |
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9th Sep 2017, 10:37 pm | #10 |
Pentode
Join Date: Aug 2005
Location: Shrewsbury, Shropshire, UK.
Posts: 149
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Re: Re-anodising heatsinks?
That would be ideal. There's no rush at all -- the PSU for this amplifier needs some re-design and a new PCB and there are still some components to source.
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10th Sep 2017, 11:34 am | #11 |
Retired Dormant Member
Join Date: Dec 2007
Location: Shropshire, UK.
Posts: 3,051
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Re: Re-anodising heatsinks?
Being amphoteric, it's difficult to predict how the aluminium oxide will have reacted, but there's a fair chance that it's just the dye which has been leached out. I'd be inclined to dump the heatsink in a hot dye bath for a few hours before contemplating anything more drastic.
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10th Sep 2017, 12:27 pm | #12 | |
Octode
Join Date: Jan 2004
Location: Southport, Merseyside, UK.
Posts: 1,156
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Re: Re-anodising heatsinks?
Quote:
John |
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11th Sep 2017, 5:43 am | #13 |
Dekatron
Join Date: Apr 2009
Location: Oxfordshire, UK.
Posts: 4,934
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Re: Re-anodising heatsinks?
My understanding is that the conditions chosen for anodising intentionally create a porous oxide layer and the dye goes in to the pores. That is then is sealed in by the action of the subsequent immersion in boiling water which "seals" the pores, though I guess the same could be done electrolytically.
B
__________________
Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch. |
11th Sep 2017, 8:52 am | #14 |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,982
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Re: Re-anodising heatsinks?
The reason that anodised aluminium cannot be used in ultra high vacuum systems is the pores. These give rise to what is known as a "virtual leak". In other words it has the characteristics of a leak, preventing the vacuum level to be attained, but in fact it is something in the chamber outgassing. And anodised aluminium outgasses pretty much forever.
The aluminium treatment for UHV use is electropolishing. For decorative use (ie not vacuum use!) electropolishing and then anodising (and dying) gives a superb mirror like finish. |
11th Sep 2017, 5:57 pm | #15 |
Pentode
Join Date: Aug 2005
Location: Shrewsbury, Shropshire, UK.
Posts: 149
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Re: Re-anodising heatsinks?
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12th Sep 2017, 8:00 am | #16 |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,982
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Re: Re-anodising heatsinks?
I've used these guys on a number of occasions, and found them to be pretty good. Perhaps worth a try. Based in Uxbridge.
http://www.metroplating.co.uk/ |
12th Sep 2017, 8:35 am | #17 |
Heptode
Join Date: Jul 2014
Location: Boston, Lincolnshire, UK.
Posts: 995
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Re: Re-anodising heatsinks?
That's an excellent link Craig - if you click on the various services they offer, they give some very good concise descriptions of each of the anodising processes.
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12th Sep 2017, 4:34 pm | #18 |
Hexode
Join Date: Dec 2005
Location: Nr. York, North Yorkshire, UK.
Posts: 348
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Re: Re-anodising heatsinks?
Hello
This sounds like something that motorbike customizers or restorers would need doing. Perhaps if you could get a read of the adds in a 'bike magazine there might be some firms that would do a small job. Just a ramdom thought. Will |
12th Sep 2017, 6:11 pm | #19 |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,982
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Re: Re-anodising heatsinks?
A guy I know in Sweden has a plater that takes a black anodised heatsink, strips the anodising and then gold plates it. Must ask him who does this, hopefully in a cost effective way.
This is what his gear looks like |
12th Sep 2017, 9:03 pm | #20 |
Guest
Posts: n/a
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Re: Re-anodising heatsinks?
We use metro plating, they are a friendly bunch, worth having a chat at tea time (10 am) outside (fag break) for a "private job". One of the cleanest plating plants I have ever seen.
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