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Author: Subject: looking for something that resists acids and chemical attack.
CHRIS25
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[*] posted on 8-4-2012 at 13:19
looking for something that resists acids and chemical attack.


Hi, I need to place copper in quite corrosive solutions, one of these is a copper chloride made with Hcl and Hydrogen peroxide for example. But only parts of the copper are to be attacked. I have tried a Red Permanent marker and drawn over the areas that are to be left untouched by the solution. this works very well except that it lacks a degree of accuracy but most of all won't resist for longer than an hour or so and begins itself to dissolve. Black does not work for more than 10 minutes (anyone suggest why)? Anyway some novel thing that I could paste/place/draw onto copper to prevent attack when it is submerged into very strong oxidising or destructive solutions.

My lack of knowledge of chemistry prevents me from even having ideas about what I can experiment with. Thanks guys for your help.
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AndersHoveland
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[*] posted on 8-4-2012 at 13:47


petroleum jelly or wax

[Edited on 8-4-2012 by AndersHoveland]
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AJKOER
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[*] posted on 8-4-2012 at 13:58


Here is an idea. Gold plate the copper and scrap off the areas to be attacked. May work long enough.

When done, dissolve the Au to recycle for the next project.
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BromicAcid
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[*] posted on 8-4-2012 at 13:59


When I did electroetching of copper I used clear packing tape but it stuck too well and was hard to remove, I ended up using sticky drawer liner for kitchen cabinets and that worked great. If you use it for too long though I am sure it will start to peel up at the edges.

BTW: Are you making circuit boards?

[Edited on 4/8/2012 by BromicAcid]




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AndersHoveland
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[*] posted on 8-4-2012 at 14:13


Quote: Originally posted by AJKOER  
Here is an idea. Gold plate the copper and scrap off the areas to be attacked.

Probably would not work. Aqueous solutions of chlorine are corrosive to gold, the same may possibly be true of chloride ions with H2O2, especially if acidified.
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nora_summers
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[*] posted on 8-4-2012 at 15:19


there is lots of resources for "PCB etching" which is what they do to etch copper boards to make the printed circuits in electronics. You can get very intricate patterns with various techniques. "Toner transfer" and "photoresist" methods are the most common ones.


i'm not sure if it'll work for your specific application but it's worth googling.
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peach
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[*] posted on 8-4-2012 at 15:48


Quote:
Black does not work for more than 10 minutes (anyone suggest why)?


Is it the same brand of pen?

The marker pen method is quite common in electronics, where the etch is FeCl3 or persulphate. Although, the parts usually don't need an hour in there.

Quote: Originally posted by AndersHoveland  
petroleum jelly or wax


That is a decent suggestion, depending on how precise it needs to be.

There is a group of materials called the super acids, with the first being called 'magic'. It was demonstrated by dipping a candle in, the wax reacting with the acid, something a normal acid wouldn't do. To achieve that feat, the strongest has a pH of -28, making it over a trillion times stronger than concentrated sulphuric.

If the surface is flat, the transfers may work. You print them on a laser printer. The toner in a laser printer / photocopier is carbon mixed with very low melting plastic. You place the transfer on the copper, warm it up with an iron and then peel it back off, leaving the design printed - in theory.

The number of poor results I had with transfer paper was not funny. I was using Press And Peel and a Brother laser. Tried all kinds of things (scrubbing the board with emery and rinsing it with acetone, only ever touching it with gloves on, spreading the heat with plates).

You could also look at using a paintable mask, like liquid masking tape, tipex or liquid rubber. As every solvent sniffer nose, tipex is solvent based (or was when it was any fun), so it should be possible to rinse it back off without scrubbing at the surface. There is water based tipex out there. Beware. Not only will it come off in the bath, it's absolutely rubbish for whiting out (pen comes through it, takes an entire lesson to dry).

Polyurethane and epoxy paint is really resistant, but that may be an issue when it comes to getting it back off without damaging the rest of the finish.

The photoresist idea is also good. You only need a light box to expose it, with the design printed on a sheet of overhead projector film sandwiched between the two. I think some people use their scanner to do it, since the bulb is so bright. I actually have a new can of the sprayable photoresist in my vast collection of 'junk'.

Making PCBs was one of the topics we did in DT at school. From memory, it only had three tracks on it. The boards came with sticky back plastic over the copper. We then used scalpels to slice through it and peeled away the areas we wanted etching. Worked nicely. The circuit was a transistor based bike / bag / shed alarm.

[Edited on 9-4-2012 by peach]
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CHRIS25
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[*] posted on 9-4-2012 at 02:37


Hi guys, Well the gold is out of the question. The pcb etching sites I have read, but my pieces are never flat. The red pen is exactly the same make as the black pen. I think that the wax petroleum jelly sounds the best. Yes it is important to be able to wash off any resist that I put on the copper because that part that was covered will then be treated with heat, and the borax solution can be safely pasted over the previously treated chemical part and then washed off with water.

I am not aware of any brand in Ireland that is pure petroleum jelly. When you say wax, do you mean candle wax or polishing or bees wax, the latter I know is very expensive.

Ok, thankyou.
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peach
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[*] posted on 9-4-2012 at 04:31


Candle wax.

I kept bees for a while, and still have mountains of hives, a few bee suits, tools, smoker, comb spinner etc. Thorne is a popular UK supplier of all things bee related. They also sell the returned wax it's self, £4.20 for 500g.*

A problem with the marker pens is that the pen really needs building up, as it's so thin and watery that the fibres in the nib tend to leave microscopic streaks in it. Another problem is, building it up, as the ink can partially redissolve the layer it's going onto, cutting through it again. Use a really decent marker pen, so it's pigment heavy and covers. Let it dry completely and then, very, very gently, barely touching the surface, go back over it. It might work better if you squeeze the pen out and use a tiny, soft brush.

A badly mangled comb preform and some wax recovered from melting out old combs:


*UK bee keepers tend to make the whole affair much more money oriented, expensive and complex than it really is. The bees will, largely, look after themselves. All they really need is a box with combs in it. Given where you live, it could be something you could set up. Buy things from Poland. It's about 75% cheaper and I prefer my Polish beesuit to the £100+ ones from Thorne.

[Edited on 9-4-2012 by peach]
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CHRIS25
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[*] posted on 9-4-2012 at 05:03


Hi Peach,

interesting photo, I love eating that stuff. So you kept bees? How many stings have you had? A good idea about the red pen. Hence my original question, the red ink left me with small amounts of pitted copper and not so wll defined outlines, but I will try the paintbrush idea and take things a little more slowly, experiment time again.
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watson.fawkes
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[*] posted on 9-4-2012 at 05:20


Quote: Originally posted by CHRIS25  
Yes it is important to be able to wash off any resist that I put on the copper
Shellac. Washable with simple alcohols. It's cheaper to buy flake and dissolve it yourself. You'll likely want a marker pigment, like TiO2. You can apply it with a paintbrush or spray. Any non-reactive lacquer would work, really, but the solvents to take them off aren't as kind as for shellac.
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CHRIS25
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[*] posted on 9-4-2012 at 05:44


I have seen shellac mentioned many times. But as with so many things here in Ireland It is no where to be found and postage to Southern Ireland is always horrendous from UK and USA. My wife has to order from Uk and Holland just to get craft materials and soap making stuff?!?!?!?!?!?!

But thankyou watson fawkes
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[*] posted on 9-4-2012 at 05:53


Quote:
interesting photo, I love eating that stuff. So you kept bees? How many stings have you had?


There are can be tens of thousands of honey bees per hive but, provided you don't annoy them too much by squashing their friends, they're not all that bothered, particularly if they're used to regular visits and are busy with the honey. Their hive like behaviour, order and information sharing is only really appreciated in person.

Shellac is a good idea.

If you want something more off the shelf, how about one of those tiny tins of enamel paint from an AirFix model shop? The normal colours are about £1.25. You can also get clear coat which would be less of a problem to remove (visibly speaking), but it'd be harder to see when masking. Some of the discount shops sell larger tins for the same price. Cleans up with mineral spirits / turps. Rather than rub at the surface, I'd dunk the piece and let it soak back off.

[Edited on 9-4-2012 by peach]
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[*] posted on 9-4-2012 at 07:10


You might also be able to get some from a luthier if there are any violin shops around.
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watson.fawkes
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[*] posted on 9-4-2012 at 07:11


Quote: Originally posted by CHRIS25  
But as with so many things here in Ireland It is no where to be found
You must not have looked very hard. Any supplier to fine woodworkers will carry it. It's still used commonly as a sealer for resinous woods and plaster. "Bulls Eye" is one retail brand (already dissolved); I'd find it hard to imagine one of the major retailers in Ireland doesn't carry it. The flake has indefinite shelf life, but the pre-dissolved versions don't.
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[*] posted on 9-4-2012 at 08:02


Teflon is usually the standard for chemical resistance . . .try perhaps wrapping your copper in some of that thick PTFE tape sold at hardware stores. Teflon does sometimes react with particular reagents, but for most chemicals it'll perform very well.



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CHRIS25
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[*] posted on 9-4-2012 at 08:04


Watson.fawkes thanks but I am totally ignorant about woodwork, don't even know the difference between hard and soft wood, and my son sticks up all the IKEA stuff. So would have no idea that I could get something from them. I will see about the airfix paints, though I read on a couple sites where they recommend ingredients that I really don't know what they mean they keep referring to Red strangely enough. there must be something about that colour's chemical makeup. Ok first try and find shellac, it's apparently also good for sealing the colours from further oxidation, although this refers to years rather than days or months.
Thanks.
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[*] posted on 9-4-2012 at 08:18


IKEA: noun, a maze from some wacky 1960's Mk Ultra experiment.

Quote:
there must be something about that colour's chemical makeup


I have never looked into it in detail, but red paint is apparently much more susceptible to UV damage than the others. My own car has turned a reddy pink, been t-cut back to red, then gone back to reddy pink. I've seen it on lots of other red cars and my neighbour's feelings were, "Oh....... I'd never buy a red car."

Quote:
Ok first try and find shellac


Hit the yellow pages and look for carpenters, particularly those who make custom furniture. Ask them if they have any spare you could buy, or if they know where to get it. There will be people around with it.

The process of applying Shellac is called 'French Polishing'.

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CHRIS25
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[*] posted on 9-4-2012 at 08:27


Ohh French polishing yep have heard about but never knew what it was. Carpenters it is then. Thankyou. Did'nt get the IKEA joke by the way. Well sort of, but what is MK ultra experiment?
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[*] posted on 9-4-2012 at 09:21


Mk Ultra was a mind control project run by the CIA around the 60's and 70's, when they experimented with the onslaught of newly available psychotropic drugs to see if they could be used as weapons, for wiping memories, implanting subconscious suggestions (sleeper agents), telekenesis, telepathy or to undermine a public figures social position (e.g. slipping LSD into their water supply). They, if some are to be believed, conducted numerous weird, weird experiments, such as putting people into insulin induced comas or making them listen to the same sentence on repeat for 18 hours a day, for a month solid. That is much akin to my experiences of shopping in Ikea.

[Edited on 9-4-2012 by peach]
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CHRIS25
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[*] posted on 9-4-2012 at 09:47


Ok Got it - funny
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[*] posted on 11-4-2012 at 16:07


I use woman's nail polish for many of my circuit boards.
Try a dollar store ,
I've noticed the ones with polyurethane to be a lot more chemically resistant than others.
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CHRIS25
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[*] posted on 12-4-2012 at 00:13


Quote: Originally posted by h2o2guru  
I use woman's nail polish for many of my circuit boards.
Try a dollar store ,
I've noticed the ones with polyurethane to be a lot more chemically resistant than others.


Yes but circuit boards are not for aesthetic purposes. seriously though, thanks, but I have used nail varnish, it really darkens most patinas and takes away the hard work done to achieve just the right tone. I have read about shellac and was pleased to see that it does not affect the actual colours on the copper. So I can use it for dual purpose.

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