Author Topic: Copper thermal collector- Not paint ideas to make it black?  (Read 15273 times)

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madlabs

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Hi All,

I have a bunch of older thermal panels, copper sheet with molded copper piping. They keep popping and I'm tired of brazing them only to have them fail elsewhere. The trouble is that the copper has become thin from erosion/corrosion. I think they were thin when I got them and hot tub duty (this is for my hillbilly hot tub) is hard on copper, what with the bromine.

Anyway, I'm going to try brazing some soft copper tube on to the collector plates and in doing so will totally screw up the anodized (I think) finish. Of course I can paint it black, but we all know paint isn't the best thing to use. So, are there any sorta simple, sorta cheap ways to put a black finish on after I braze that isn't paint?

Thanks!

Jonathan

DamonHD

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #1 on: May 01, 2014, 02:27:45 PM »
Soot?

From a hillbilly BBQ?

Rgds

Damon

madlabs

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #2 on: May 01, 2014, 04:01:19 PM »
Ha! Wish that would work. We got plenty of soot in the wood burning heater from the hot tub, let alone the BBQ and burn pile!

JOnathan

dbcollen

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #3 on: May 01, 2014, 09:57:31 PM »
if you have a source for tannic acid such as walnut husks, or oak leaf or sawdust tea, boiled till concentrated, it should stain the copper black.

Bruce S

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #4 on: May 02, 2014, 07:26:49 AM »
if you have a source for tannic acid such as walnut husks, or oak leaf or sawdust tea, boiled till concentrated, it should stain the copper black.
What he said  ;D , just remember to wear multiple gloves as this will stain everything else too.
We've used the walnut husks for stuff, but I've had great luck with the high heat version of flat black paints usually used for car engines.
 
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madlabs

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #5 on: May 02, 2014, 08:37:33 AM »
Hmmm, I do have access to oak leaves and sawdust piles. Manzanita trees too, they have lots of tannin. So does ceder. I'll have to do a spot test and see if it works. Wonder how it would hold up long term?

Bruce, I really have no problem using paint. It's just that it is an insulator and I was hoping there would be a chemical process that I could do.

Jonathan

Bruce S

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #6 on: May 02, 2014, 09:06:05 AM »
I whole heartily agree with using natural stuff!!
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dnix71

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #7 on: May 04, 2014, 10:58:58 AM »
http://www.wikihow.com/Darken-Copper

4 ways. Palmolive dishwashing liquid has sodium bisulfite in some formulations. The sulfite will blacken copper quickly.

We use selenious acid paste at work to black brass name plaques.

madlabs

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #8 on: May 05, 2014, 08:26:28 AM »
Dinx,

The liver of sulfur looks good! I'll order some and give it a shot. Hopefully it is a very deep black.

Thanks!

Jonathan

hiker

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #9 on: May 05, 2014, 11:14:38 AM »
might try a gun shop--they have brass bluing kits..comes out looking black..should work on copper ?
WILD in ALASKA

madlabs

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #10 on: May 06, 2014, 01:29:43 PM »
Good idea. A pal of mine is a gunsmith, I'll ask him.

Jonathan

Frank S

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MattM

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #12 on: May 06, 2014, 10:17:25 PM »
If you use distilled water you shouldn't burn through copper.  Most people make the mistake of using bleach water in copper.  Bleach/Chlorox is corrosive to copper.  Distilled water is inert and won't interact with the copper whereas tap water is often contaminated with either chlorine or fluoride, both corrosive.

madlabs

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #13 on: May 07, 2014, 05:58:11 PM »
Frank, they do make a product that looks like it should work on copper! Only thing is they don't have a price, it says call for a quote, which is always scary. They are closed right now and I'm going out of town for a few days, but I'll call 'em, looks real good and thanks.

Matt, if you are talking about my using the panles wearing 'em out, these are used for a hot tub, so no way to use distilled water and there will always be bromine.

My first attempt at brazing a new tube to the surface didn't work out so well. Got some practicing to do.

Thanks all!

Jonathan

Frank S

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #14 on: May 07, 2014, 07:56:41 PM »
Johnathan I don't know which filler you are using but Sil-fos™ products are specially formulated for joining copper and copper alloys .
I use  the higher phosphorous content for copper but lower phosphorous content and a secondary flux for joining copper to brass or bronze. If brazing stainless to copper use something like one of the JMM Easy-Flo grades.

http://www.jm-metaljoining.com/onlinepdf.asp?chartid=10&id=18


I used to have a price list for the Instablack and other coatings they sell. Over in Kuwait we used some of their products for cold plating   but this was years ago. I guess I am still on their mailing list
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madlabs

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #15 on: May 08, 2014, 07:56:47 AM »
Frank,

Aha. You may be on to something there. I am using general purpose rod. (Brazing newbie, if you couldn't tell) Do you know of a US distributer of the rods you linked? And it says that for copper alloys I do need flux? The tube is pure copper, but from the color of the panels when I wire wheel it to clean I'd say it has a little something else in there.

Thanks!

Jonathan

Frank S

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #16 on: May 08, 2014, 09:56:09 AM »
Frank,

Aha. You may be on to something there. I am using general purpose rod. (Brazing newbie, if you couldn't tell) Do you know of a US distributer of the rods you linked? And it says that for copper alloys I do need flux? The tube is pure copper, but from the color of the panels when I wire wheel it to clean I'd say it has a little something else in there.

Thanks!

Jonathan

 I would suggest you have a look at their home page
http://silfos.com/
 then look to the left side in the menu block download the selection guide and the PDF to joining technologies
 then at the bottom of the page there is a state by state reseller locator.
 Lucas-Mlihaupt is just one of several manufactures of silver braze/solder fillers but they are world known and many welding supply distributors carry their products even some of the box stores & hardware stores will have a limited stock.
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Frank S

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #17 on: May 08, 2014, 10:43:58 AM »
Johnathan; When brazing copper, or one or more of the alloys of copper & other metals together there is a fine line between a good stable connection and a poor one. Consideration of how the finished product is going to be used is the primary factor. For instance will the joint be subjected to stresses of movement, extreme temperatures, pressures, vibrations, tension, torsion, compression, ETC.
 Or a combination of these factors, and when the possibility of dissimilar metals will be joined the fillers & flux must be selected according to application.
 One huge mistake many people make whether they are novices or very experienced is too little or too much heat. The next biggest mistake particularly when flame brazing or welding is they get their flame too oxygen rich, this can burn the metals and or create oxides in the joint itself. in the case of copper to other alloys the contaminant is called phosphides  created by the phosphorus in the alloys.
 Set the flame on your torch so you can see a slightly cooler blue feather. it is also best if you have your regulators set to very low pressure just a little higher than needed to produce the desired flame size this gives you better fine adjustment control over your flame
 Hope this helps in someway
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XeonPony

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #18 on: May 08, 2014, 02:58:24 PM »
95/5 copper phosphorous, it will be a single shot (As in don't screw up) just make sure all the copper is clean, heat to red hot, slightly on the bright side, when you tap the rod to the copper it should instantly flow like water when you got the right heat.

for your final connections if you need high temp connections use 15% silver, copper, phosphorous as it is easier to re flow.

as frank said for multi metal use 45% silver copper phosphorous and ISO-1000 brazing flux
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bart

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #19 on: May 08, 2014, 04:29:51 PM »
   Any HVAC or welding supply should carry the Sil-Flos.  What I do is as heat is being applied melt a little of the sil-flos on the joint and when it flows, your heat is correct.

madlabs

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #20 on: May 09, 2014, 07:20:54 PM »
Thanks for the advice guys. Out of town and trying to read on my phone. When I'm home Sunday i'll reread and look for the right stuff.

XeonPony

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #21 on: May 13, 2014, 03:07:17 PM »
   Any HVAC or welding supply should carry the Sil-Flos.  What I do is as heat is being applied melt a little of the sil-flos on the joint and when it flows, your heat is correct.

not a good way to do it, as you can create head aches that way, once glowing red gently strick the stick against the pipe, when it melts and flows the second it hits the pipe you're at a temp where it will flow to the joint, once filled run the tourch to wards the back of the swedge to ensure full coverage, bit of an art to it but after a dozen joints it will be second nature.
Ignorance is not bliss, You may not know there is a semie behind you but you'll still be a hood ornimant!

Nothing fails like prayer, Two hands clasped in work will achieve more in a minute then a billion will in a melenia in prayer. In other words go out and do some real good by helping!

bart

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #22 on: May 13, 2014, 04:09:10 PM »
   Were gonna have to agree to disagree.  Done a ton of joints this way with no problems. Yes no, matter how you do it, you gotta move the torch. Not a fan of cherry red copper, esp. in when its bright out as your just to hot.

XeonPony

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #23 on: May 21, 2014, 09:42:47 PM »
not when using 95/5 copper phosphorous, if you don't have the joint temp good and hot you'll end up with a mediocre joint, I don thousands of them, and I have cut in half well over fifty of them just to see how the different temps/fluxes/torch movements made.

When you add a glob the heat of the flame will melt it long befor the joint is at optimum flow point. By striking the rod against the joint tells you when you hit the perfect temp as it will immediately flow and surficate the pipe. you may have figured out a trick, but for people not overtly skilled in gas brazing best stick with the more solid ways. reason we use air acetylene (Or in my case oxy acetylene) when doing refrigeration!

15% you can go a hair cooler due to the silver component, the 45% cooler still due to the higher silver content. Harris 8 colder yet as it is a totally different alloy
Ignorance is not bliss, You may not know there is a semie behind you but you'll still be a hood ornimant!

Nothing fails like prayer, Two hands clasped in work will achieve more in a minute then a billion will in a melenia in prayer. In other words go out and do some real good by helping!

bart

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #24 on: May 22, 2014, 03:52:03 AM »
   Are you still beating this horse?
I use 15 %.

madlabs

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #25 on: May 22, 2014, 08:48:43 AM »
I got some sil-fos rods. What about when trying to repair weak and thin surfaces? I'm not just joining pipe, I also want to try to repair some of the panels, now that I the right stuff. So I want to be able to build it up a little. I'm worried that red hot will melt through some of the weaker areas.

Thanks!

Jonathan

bart

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #26 on: May 22, 2014, 04:59:07 PM »
   Most definitely will reinforce thinner copper. But, you need to have the copper sanded nice and shiny. Start where you have good copper, just enough heat to flow well and the sil-flos will follow the torch.  Do not run a sharp blue flame. You want it to be "feathered" out. Keep the flame moving about. Keep going from good to bad until it gets built up.
   Now if you blow a hole, you can make a patch out of copper sheet or other tubing and repair it with the sil-flos.
Hope you bought the 15%, as it is great to work with.

madlabs

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #27 on: May 22, 2014, 07:24:21 PM »
Well, looking at the label, it says: "super Sil-Flo" premium oxy-acetylene welding rod and then underneath it says Substitue for 6% to 15% silver content brazing alloys. Hmm, sounds like it's not the real deal? It's made by Forney and is catalog # 48571.

Hope this is good stuff, it's what I could find locally. If it sucks I can wait and order something better.

Thanks!

JOnathan

bart

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #28 on: May 22, 2014, 07:56:08 PM »
   Never used it and from a very brief search, it ain't Sil-flos. Got no silver in it.
Here's the one I use: SIL-FOS® 15

http://www.silfos.com/htmdocs/product_support/alloy_selection_guide.html

  To the left is is a "How to". Better explanation Than I gave.

madlabs

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Re: Copper thermal collector- Not paint ideas to make it black?
« Reply #29 on: May 24, 2014, 02:37:50 PM »
Holy Cow! Now I see why they make a substitute for sil-fos! Very, very expensive. The stuff I have is better than regular brazing rod for sure. I'll see if I can muscle up the cash to get the "real deal". Thanks for the advice!

Jonathan