UK Vintage Radio Repair and Restoration Discussion Forum

UK Vintage Radio Repair and Restoration Discussion Forum (https://www.vintage-radio.net/forum/index.php)
-   Cabinet and Chassis Restoration and Refinishing (https://www.vintage-radio.net/forum/forumdisplay.php?f=21)
-   -   Re-anodising heatsinks? (https://www.vintage-radio.net/forum/showthread.php?t=139689)

GW4FRX 9th Sep 2017 3:53 pm

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?

kalee20 9th Sep 2017 4:33 pm

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!

GW4FRX 9th Sep 2017 5:05 pm

Re: Re-anodising heatsinks?
 
Quote:

Originally Posted by kalee20 (Post 974411)
The alkaline solution of dishwasher tablets attacks aluminium, as you've found out! Depending on how bad the surface is, you may be lucky.

Oh well. I learned a lesson from that :censored: 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...

Craig Sawyers 9th Sep 2017 7:11 pm

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.

Tractionist 9th Sep 2017 7:19 pm

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 ..............

GW4FRX 9th Sep 2017 7:54 pm

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.

Bazz4CQJ 9th Sep 2017 8:33 pm

Re: Re-anodising heatsinks?
 
1 Attachment(s)
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

kalee20 9th Sep 2017 9:24 pm

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.

GW4FRX 9th Sep 2017 10:32 pm

Re: Re-anodising heatsinks?
 
Quote:

Originally Posted by Bazz4CQJ (Post 974470)
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

I quite often put passivated steel chassis items for restoration (such as Racal receiver side panels or bottom chassis members) in the dishwasher. They come out looking like brand-new. But aluminium heatsinks evidently don't, alas.

Not sure the homebrew option would go down very well with Madam or the elf 'n' safety people nowadays....

GW4FRX 9th Sep 2017 10:37 pm

Re: Re-anodising heatsinks?
 
Quote:

Originally Posted by kalee20 (Post 974477)
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.

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.

dseymo1 10th Sep 2017 11:34 am

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.

John M0GLN 10th Sep 2017 12:27 pm

Re: Re-anodising heatsinks?
 
Quote:

Originally Posted by kalee20 (Post 974477)

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!

The DIY process I used about 5 years ago required the freshly anodised article, whether natural colour or dyed, to be immersed in boiling distilled water for 30 minutes to harden it, the piece I anodised has been outside now for that period and looks as good as it did when made.

John

Bazz4CQJ 11th Sep 2017 5:43 am

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

Craig Sawyers 11th Sep 2017 8:52 am

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.

GW4FRX 11th Sep 2017 5:57 pm

Re: Re-anodising heatsinks?
 
Quote:

Originally Posted by kalee20 (Post 974477)
Look forward to what South West Metal Finishers come up with.

Unfortunately they came up with a mildly snotty reply stating that they "...do not undertake this kind of work." Oh well. Back to the Yellow Pages.

Craig Sawyers 12th Sep 2017 8:00 am

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/

Goldie99 12th Sep 2017 8:35 am

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.

Telleadict 12th Sep 2017 4:34 pm

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

Craig Sawyers 12th Sep 2017 6:11 pm

Re: Re-anodising heatsinks?
 
1 Attachment(s)
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

Guest 12th Sep 2017 9:03 pm

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.

M0FYA Andy 12th Sep 2017 9:10 pm

Re: Re-anodising heatsinks?
 
Quote:

Originally Posted by Craig Sawyers (Post 975218)
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

What a silly idea! Heatsinks are intended to dissipate heat, not just look pretty. Obviously an audiophool idea................

Andy

Craig Sawyers 13th Sep 2017 7:13 am

Re: Re-anodising heatsinks?
 
Didn't you see my earlier post regarding dissipation being almost all convection and hardly any through radiation for a temperature rise of less than 40C? The colour of the heatsink is pretty much irrelevant for a temperature rise of less than 100C.

There is another effect that reinforces this idea called the "view factor". Think about how much each part of a finned heatsink area sees of the environment, and is capable of thermally radiating. Before you get very deep into the profile, each area of the heatsink sees progressively less of the environment, and the more it sees of the adjacent fin. Since the adjacent fin is at the same temperature there can be no radiative energy transfer - it can only radiate if it sees a cooler environment which it can only peek through the gaps between the fins.

All of which says: the colour of the heatsink does not matter if you can touch the heatsink without burning yourself. Cooling is close to 100% convection.

The colour of a heatsink is traditionally black for decorative reasons only, and alas reinforces the pseudoscience argument that thermal radiation assists dissipation to a significant degree.

Here is a link to a heatsink manufacturer that says the same thing http://www.abl-heatsinks.co.uk/heats...ace-colour.htm

Quote "The heat transfer from the heatsink occurs by convection of the surrounding air, conduction through the air, and radiation. Heat transfer by radiation is a function of both the heat sink temperature, and the temperature of the surroundings that the heat sink is optically coupled with. When both of these temperatures are on the order of 0 °C to 100 °C, the contribution of radiation compared to convection is generally small, and this factor is often neglected. In this case, finned heat sinks operating in either natural-convection or forced-flow will not be effected significantly by surface emissivity."

Craig

M0FYA Andy 13th Sep 2017 7:42 am

Re: Re-anodising heatsinks?
 
OK Craig, I retreat defeated!

Andy

Craig Sawyers 13th Sep 2017 8:04 am

Re: Re-anodising heatsinks?
 
And from the Aavid heatsink manufacturer https://www.aavid.com/product-group/...ons-na/anodize

"Relatively large extrusions and those used at low temperature rise, as in many high power applications, will only gain up to 10% by the addition of an anodized surface.

With forced ventilation (using a fan) convective cooling is about 3 times higher than in natural convection. This changes the proportion of heat transfer due to radiation. An anodized finish will only add 4 -8% to the overall cooling effect in forced air. This percentage again, depends on fin spacing and heat sink dimensions. The color of the anodized finish makes little impact on emissivity since most radiational heat loss occurs at wavelengths higher than visible light.

As a thumb rule, if anodize is not required for aesthetic or corrosion protection, we suggest it only for small, open finned heat sinks in natural convection."

Craig

Craig Sawyers 13th Sep 2017 8:09 am

Re: Re-anodising heatsinks?
 
Quote:

Originally Posted by M0FYA Andy (Post 975325)
OK Craig, I retreat defeated!

Andy

Aplogies - my second post crossed with yours!

There is an application that needs 100% radiative cooling though - in space applications (where no-one can hear you scream!). Since it is in vacuum, the only method of getting heat out is via a radiator panel pointed at deep space (which is only about 2 Kelvin, so T1^4 - T2^4 is high). Each circuit board has a thermal layer connected to its housing. Each of those (there might be dozens or up to a hundred on a space vehicle) is coupled to the radiator panel with ammonia heatpipes.

Craig

Bazz4CQJ 13th Sep 2017 8:28 am

Re: Re-anodising heatsinks?
 
Quote:

Originally Posted by Craig Sawyers (Post 975331)
The color of the anodized finish makes little impact on emissivity since most radiational heat loss occurs at wavelengths higher than visible light.

You sometimes see heatsinks which have been painted black. I have always wondered about the trade off between the effect of the colour on improved radiation, and the thickness of a layer of paint reducing conductivity.

From what you say, it seems possible that painting something black could actually be detrimental from a thermal standpoint? Probably not a big effect, just a waste of time?

B

Craig Sawyers 13th Sep 2017 8:54 am

Re: Re-anodising heatsinks?
 
Well, back when I was involved in this from a production standpoint, anodising - particularly black - was a nightmare. Depending on the condition of the bath, and the repeatability of the dying and sealing processes you could get anything from a nice deep black right the way to almost a blueish tinted black.

What precise colour you get is also strongly dependent on the aluminium alloy - so that is another process to control if you aim to get colour uniformity.

In the end we had a sample and the plater had a sample. They (it wasn't Metro Plating, by the way) were told that if the batch was visually different to the sample to strip it and replate. And we did rigorous QC on goods inwards.

Powder coating can be much more predictable from a colour point of view, and with a much wider colour palette, but it is difficult to get uniform coating on sharp corners and into deep profiles (like a heatsink).

There is another sneaky problem with extruded heatsinks - they are always slighly banana shaped. It is inherent in the extrusion process. Aavid cheerfully own up to that, and say if flatness of the device mounting surface is important (and why wouldn't it be?) that it should be post-machined flat. And they will do it for you - at an additional cost.

Craig

G6Tanuki 13th Sep 2017 10:50 am

Re: Re-anodising heatsinks?
 
It's not just space-in-a-vacuum that denies cooling by convection: anywhere in zero-gravity experiences the same effect. There are lots of fans used for cooling in things like the ISS.

[Zero-gravity has other odd effects: a friend of mine is NASA's fire-suppression-in-space supremo. Without convection, fire behaves very differently in zero-G !]

Craig Sawyers 13th Sep 2017 2:21 pm

Re: Re-anodising heatsinks?
 
That is a good point. My experience is with unmanned space vehicles - I hadn't thought of cooling implications in manned zero g environments, and particularly the hazards of fire and how it behaves.

kalee20 13th Sep 2017 5:11 pm

Re: Re-anodising heatsinks?
 
1 Attachment(s)
Quote:

Originally Posted by M0FYA Andy (Post 975275)
Quote:

Originally Posted by Craig Sawyers (Post 975218)
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

What a silly idea! Heatsinks are intended to dissipate heat, not just look pretty. Obviously an audiophool idea................

Andy

Here is a selection of small heatsinks in a sample box from Aavid Thermalloy. There's black, red, blue, gold, natural, and plain. While the anodising may make only a small difference to performance, they sure do look pretty.

I used to work for a well-known power supply manufacturer, their approach with large heatsinks for highly-dissipating linear power supplies was to black powder-coat the heatsinks! As far as I know, there was no study done to determine whether plain, black anodised, or black powder-coated were best. I suspect not very much difference, as others have commented!

Diabolical Artificer 14th Sep 2017 6:27 am

Re: Re-anodising heatsinks?
 
Old car engine oil is used in metalwork to give a black finish, the only problem is this is done by heating
said metal to cherry red. Easier to achieve with steel and iron than ali. Still might be worth experimenting with a blow torch. How big is said HS?

To be honest I'd just spray it black with bog standard spray paint, doubt it'll ever get hot enough to damage the paint. Think of a car roof in summer, gets hopping on one leg waving your hand about hot.

If that don't appeal here's - https://www.ebay.co.uk/sch/i.html?_f...paint&_sacat=0 various high temp paints as found on ebay. I've used both the barrel paint and SAS 59, works ok and have also used stove paint. Both the exhaust and stove paint comes off eventually, but then both hospital hot. I've had my burner glowing orange, not blacking can survive that.

Andy.

Radio Wrangler 14th Sep 2017 7:59 am

Re: Re-anodising heatsinks?
 
There's also a guy in Sweden who takes aluminium electrolytic capacitors, de-cans them and re-homes the innards in little hardwood housings. His web pages are quite lyrical about the improvements to be obtained and the effects of different woods. No mention of life-expectancy. I'm afraid I didn't bother to save the URL when I was pointed to it.

Couldn't be the same bloke, could it? I suppose he'd have gone for Iroko heatsinks.

At least the gold plate will have virtually no effect in either direction.

David

Herald1360 14th Sep 2017 8:46 am

Re: Re-anodising heatsinks?
 
Would the recased electrolytics be any worse than old cardboard cased ones? :-)

Craig Sawyers 14th Sep 2017 10:40 am

Re: Re-anodising heatsinks?
 
Quote:

Originally Posted by Radio Wrangler (Post 975588)
There's also a guy in Sweden who takes aluminium electrolytic capacitors, de-cans them and re-homes the innards in little hardwood housings. His web pages are quite lyrical about the improvements to be obtained and the effects of different woods. No mention of life-expectancy. I'm afraid I didn't bother to save the URL when I was pointed to it.

Couldn't be the same bloke, could it? I suppose he'd have gone for Iroko heatsinks.

At least the gold plate will have virtually no effect in either direction.

David

Good grief. Sounds like the sort of hokum that gives rise to mains fuses filled with beeswax.

No - the guy I know's day job is at the Karolinska Institute carrying out research aiming at helping stroke patients recover more quickly and better by Transcranial Direct Current Stimulation.

His degree is in engineering Physics with majors in mathematics and computer science.

So a hard technologist - not a smoke and mirrors guy by any stretch

Craig

joebog1 14th Sep 2017 11:00 pm

Re: Re-anodising heatsinks?
 
8-\ That guy in sweden should rehouse some 3-1000A's in wooden cases!!!

The sound should be superb, especially in class A

Joe

GW4FRX 15th Sep 2017 7:22 pm

Re: Re-anodising heatsinks?
 
Quote:

Originally Posted by Craig Sawyers (Post 975111)
I've used these guys on a number of occasions, and found them to be pretty good. Perhaps worth a try. Based in Uxbridge.

Just to wrap the thread up, I spoke to these and a few other companies but they all wanted a three-figure sum plus VAT to do the work. I eventually found an establishment in Manchester who would do it for considerably less and seemed to know what they were talking about, so the heatsinks are currently en route for treatment.

As seems to be usual on this forum, I learned a great deal about heatsinks and heat transfer from this thread and many thanks to all for the very valuable suggestions. Every day's a schoolday :)

Craig Sawyers 15th Sep 2017 8:08 pm

Re: Re-anodising heatsinks?
 
I'd be interested in who the company in Manchester is

kalee20 16th Sep 2017 12:08 am

Re: Re-anodising heatsinks?
 
Yes - please share! (With a photo of the refurbished heatsinks!)

GW4FRX 16th Sep 2017 8:55 am

Re: Re-anodising heatsinks?
 
The company is Colour Anodising of Radcliffe, Manchester. I'll put up before-and-after pics of the results as soon as they return

Craig Sawyers 16th Sep 2017 11:19 am

Re: Re-anodising heatsinks?
 
I did a web search before you posted, found them, and discounted them - because the website looked so swish I was sure they had to be expensive!

But very interesting looking company.

Regarding gold plating, I also had a look around the UK and found http://www.goldplating1.co.uk/ in Bolton. Prices look really good - maybe I'll try a heatsink and see what they would quote for stripping and gold plating.


All times are GMT +1. The time now is 1:18 pm.

Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.