Aluminium and Ferric Chloride

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Edison finally got them to last worth a hoot, hence my term "working" light bulb. Thousands of trials later, he found tungsten. Thank you, Misters Swan and Edison.
Uncle Tom sure screwed the pooch on the AC/DC battle, though. Thank you, Misters Tesla and Westinghouse.
-- That is what learning is. You suddenly understand something you've understood all your life, but in a new way. -- Doris Lessing
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On Sat, 11 Dec 2010 09:01:28 -0800, Larry Jaques

Clever people, these Swedes! But look where it got us: They caused Global Warming!
BTW I did not know that Tesla and Westinghouse were AC/DC. I guess I did not ask and they did not tell...
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On Sat, 11 Dec 2010 18:03:20 -0800, snipped-for-privacy@gmail.com wrote:

Swedes? Swanny was a Brit. Nicolo was ascerbic. I mean a Serbian. And George 'n Tom were 'Murricans. What pooch-screwin' Swedes do you know, and how is it relevant? (Dare I ask?)

Friends of Tawms, fer sher.

William?
-- Know how to listen, and you will profit even from those who talk badly. -- Plutarch
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I don't know what you're referring to as the "back spray" step.
I suspect that the compounds that were applied to the aluminum test piece didn't actually adhere to the piece, but instead just formed a skin over the surfaces. I also suspect that if the resist had been scratched with a fingernail (even after overnight drying) it would've lifted easily from the surface. This is generally true of many coatings which feel dry to the touch, but aren't fully cured.
Aluminum oxidizes rapidly, and it's not as easy to paint as most metals. In the refinishing line of products, there are etchants used to prepare the surface for proper adhesion, such as mild phosphoric acid solutions.
The test solution's temperature of 35C/95F isn't hot, considering that many coatings that are applied for corrosion prevention/protection are cured in ovens at 180F+.
I believe that if the resist had adhered properly, the test results would've been significantly different.. or maybe that resist just isn't compatible with the ferric chloride solution (even though it is called resist).
I'd be tempted to try an etchant (metal prep - in the autobody shop supplier lingo), followed by a coating of a good resist that is air dried, then heat cured (electric heat gun pointed into a vented metal enclosure, or low temp oven), then a timed bath in the test etchant.
--
WB
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On Thu, 2 Dec 2010 23:43:56 -0500, "Wild_Bill"
Spray the reverse side of the piece so it does not etch there. I have been using a Dupli-color primer for both resist and back-spray. This works fine up to about 40 minutes of etch at 35 degC in FeCl3. If the etch goes longer the primer begins to detach. 30 - 40 minutes is not enough to get deep enough etch in brass, let alone steel. Hence looking for different preparations.
Asphaltum based resists are pretty much the old industry standard. I could buy one but I am cheap. I know people make their own. I tried dissolving a chunk of asphaltum which I bought some time ago for roof repair. The first time I just tried to dissolve it in cold Varsol. It was not particularly successful. This time I warmed up the Varsol and got much more of the asphaltum into the solution. However, as I mentioned in the OP, it dries soft and is prone to accidental damage (some can be seen on the pics). I suspect it is due to the additives in the asphaltum prep I was using. I just have not got around to digging up some asphaltum from a road.
There are many alternatives and within the limitations mentioned above the Dupli-color primer has been pretty much the best I have tried so far, at least on brass, copper and steel. It has its issues, too: I believe that it has a limited shelf life, for instance, but that's not a problem if one uses a lot.

The whole point is that this reaction is *exothermic* and the solution was *boiling* by the time I got to interfere, i.e. 100 degC. So the resist was pretty much liquid and the back spray "burned' off. Note that only a part of the back spray peeled off completely, the "marbled" portion was still covered and I had to remove this cover by pretty vigorous application of acetone.

The problem with that is that you do not want to screw up the surface underneath the resist and you need to be able to get the pattern into the resist. For instance the back spray I used was too hard for that and would have been useless as a resist.
Michael Koblic, Campbell River, BC
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I wonder if you might find (or maybe you have) old techniques for etching aluminum in some old books from say, the 1920s-40s.
A lot of machine labels/placards were made from thin sheetmetals by etching away much of the surface to leave raised text and symbols (and some fairly small text at that). The etched areas were often then filled with paint for contrast. A lot of those etchings were brass, but I've found many smaller ones, such as those found on old power tools, which were aluminum.
I got the part about the reaction and the heat. If the resist had stayed in place (in a diluted or buffered etchant solution), you may have achieved results more to your liking.
When the resist has poor adhesion, any type of etchant is free to wick under the resist and migrate freely, essentially sucked in by the capillary action of the fine scratches.
There is a term in refinishing techniques that describes a problem that arises from using coatings that aren't properly reduced/thinned properly. When a coating is too thick to wet the surface properly, bridging occurs. Bridging is when the coating forms a skin on the work surface, but doesn't penetrate down into the valleys of the sanded surface. The result is air paths under the coating, and will lead to serious problems with subsequent applications of coatings (additional primer or paint). Bridging usually isn't a problem with aerosol rattlepaint, as there generally isn't a high concentration of solids in the product.. but it can happen.
The phosphoric etchant solutions I referred to are mild, and don't really attack the aluminum aggressively.. instead, they mostly just clean the surface of all oxidation. If the diluted metal prep were applied to a high polish/mirror finish, it would dull it slightly, but not pit or erode it. If a high polish finish were desired, the polishing would be done after etching.
There are primers that are called etching primers (aerosol or bulk), which I believe are intended to result in better adhesion, but I haven't investigated the actual process of their etching properties. I'd guess the etchant would be completely different than the water-based types I've used in the past, as the solvents need to flash and evaporate quickly.
I think I recall that you've described some electroetch techniques, but I don't remember if you had tried them, or were investigating them.
Have you tried to apply any of the laser printer toners as resist, by printing a mirror image and then transferring it to the workpieces? If an accurate image is difficult to produce, then omitting the characters and just cover the workpiece, so you could carve out the characters by hand (if that's your usual method). This process has been used for quite a long time for etching relatively fine detail printed circuit boards. The transferred toner adheres well, but it's also a very thin coating.
When folks here in RCM discuss rugged coatings, they often mention spray-on truck bed liner. I would imagine that the cure time is long, and workpieces might need to be coated well in advance. I haven't used these products, and at least one user has commented that surface prep isn't absolutely required, but proper surface prep nearly always improves proper adhesion.
Another product that's highly regarded as a good corrosion preventive coating is the line of POR coatings, so that may be another option.
Any material that's used for resist should receive the proper preparation of the surface. If proper application dictates that a primer be used, then the primer should be applied to a surface that's been prepared so that it will achieve maximum adhesion. Curing times for various coatings can vary widely.
The resist coatings shouldn't be lifting away from the workpieces because of minimal adhesion, or break down from moderate heat. Paint manufacturers test their products very aggressively for chemical resistance and durability, including elevated temperatures.
Before the nasty multi-part paint formulas (hardeners, catalysts), heat was the most common method of force-curing paints. Heat will dramatically increase the durability/toughness of common paint coatings. For home shop curing, a heat gun or even an incandescent light bulb in a small fire-proof (metal) enclosure will be sufficient. Of course, the sun also works remarkably well, some days.. and much faster with dark colors. The vapors should be vented outdoors thru an appropriate/safe venting syatem when primers and paints are applied indoors.
--
WB
.........


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A lot of the plates were magnesium as well. I have several from the machines that I defined and bought by piece and wire and IC.
Those were the days - Not in Engineering but a Product Development Engineer in Marketing. Without a budget, but a need and urgency I bought almost all of the machines - engineering bought several of the Gate Arrays needed that were minimum order and out of my signing level.
The issues with ferrous enchants is the heat generated locally. We bought ours - like pinstripes 2" wide - lines and words.
Martin
On 12/3/2010 11:05 AM, Wild_Bill wrote:

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On Fri, 3 Dec 2010 12:05:58 -0500, "Wild_Bill"

Sometimes it works like that, sometimes it does not. These are some of the better ones: I left the numbers covered and put patina on the etched part:
http://www.flickr.com/photos/27683124@N07/2889429630/in/set-72157605638700703 / http://www.flickr.com/photos/27683124@N07/2588780561/in/set-72157605638700703 /
The second one looked better in reality than its photo (scanned 35mm - a very old picture)
I was less happy trying this in steel:
http://www.flickr.com/photos/27683124@N07/2582180479/in/set-72157605638700703 / http://www.flickr.com/photos/27683124@N07/2716088956/in/set-72157605638700703 /

That is indeed an issue.

I think it does - sometimes.

Only if you get a deep enough etch - not, apparently, a problem with aluminum :-)

They work fine on brass. I get much deeper etch on steel than with FeCl3 but also a lot of foul-biting. There is much work to be done there: I am not sure if this is a function of the current strength (does high current warm up the metal surface and promote lifting of the resist?), electrolyte strength (I got definitely better results with weaker salt solution than with a concentrated one which seemed to attack the resist all of its own), gas production (?), resists behaving differently when exposed to electric current as opposed to FeCl3, etc.

This is a pretty good method as long as one uses Press-n-Peel and HP laser printer (Brother won't work, something to do with their toner). Also, most of the hobby methods of transferring the pattern I have seen described do not work - I developed one of my own. Interestingly it is easier to get fine detail transferred than to get a wide area coverage. You have to re-touch - always. Most of my recent stuff has been done this way:
http://www.flickr.com/photos/27683124@N07/5069134153/in/set-72157605638700703 / http://www.flickr.com/photos/27683124@N07/4996861153/in/set-72157605638700703 /
There are other techniques, of course, which work fine:
http://www.flickr.com/photos/27683124@N07/4358722420/in/set-72157605638700703 /
in spite of all the circular ridges due to crappy turning bridging did not seem to be a problem in this instance.
And then there is cheating:
http://www.flickr.com/photos/27683124@N07/5034765434/in/set-72157605638700703 /

How many spray can paints will withstand boiling acid?
Michael Koblic, Campbell River, BC
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I like your various uses of combining different metal finishes, and also different types of hardware in your many varied designs. The sundials are attractive in methods of design, and complemented by the various finishes and metals used to construct them.
This one has very sharply defined characters with high contrast http://www.flickr.com/photos/27683124@N07/2582180545/in/set-72157605638700703 /
My mention of diluted phosphoric acid solutions (metal prep) was wrt aluminum surface preparation prior to applying a primer, which will ensure the best possible adhesion by removing all oxidation, much more effectively and thoroughly than sanding with fine abrasive and wiping the workpiece with solvent/acetone. The results will be improved adhesion.
As far as aerosol rattlepaint that's acid resistant at temperatures near the boiling point, I've never tried that test. I know that many paints are more sensitive to solvents such as naptha, brake fluid, gasoline, etc, even at moderately cool temperatures.
Paints are essentially plastic skin, and many plastics are highly resistant to acids, as we've seen by acids being packaged in plastic containers. The heat aspect adds a more severe element, but 212F isn't extremely hot, considering that many paints are force cured at 180F+.
Then the question would be how long does the paint need to be resistant to the acid and heat.
Improperly applied and uncured paint will definitely fail fairly quickly (even without the acid). That's why I was suggesting that the aluminum workpieces be properly prepared with a phosphoric acid wash to remove all oxidation prior to application of the primer. After the primer has been heat cured, a coat of paint can be applied, which should also be heat cured. The result of proper surface preparation and cured coatings is a tough, durable protective skin that's fully adhered/bonded to the workpiece. The acid isn't going to eat/melt the paint, and the heat isn't going to cause the primer to instantly separate from the aluminum surface since it's bonded to the metal because proper prep procedures were followed. If the acid can't get between the primer and the aluminum surface, it's not going to take the paint off. I would expect some tests will result in undercutting near the edges of the protective coatings, and that variable will likely be difficult to predict or prevent.
I have experience with the previously mentioned prep methods, and they are standard preparation and finishing steps that have been used for decades in nearly all areas of coatings applied in production of painted/coated metal parts. Many folks agree that a baked, factory finish isn't easily duplicated wrt durability.
I don't know which specific products to recommend for the etchants you'll be testing.
I do know the difference between the durability of properly applied coatings, compared to auto paint jobs that blow off in a car wash. I've seen this happen, and the guy's little white Buick Special was pink when the white paint actually blew off the car.
--
WB
.........


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On Sat, 4 Dec 2010 08:27:42 -0500, "Wild_Bill"

Thank you.

[...]
I spent some time today with a guy in the local paint shop. By our community standards he was not only very helpful but also knowledgeable. We went through your recommendations. The biggest problem is that the two sides of the piece have different requirements.
He made some further helpful suggestions if I want to continue to work with aluminum in future. Right now I have a few unresolved issues with the other metals so I shall shelve the aluminum for the time being. Unless I can think of something brilliant to do with it meanwhile.
Michael Koblic, Campbell River, BC
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On Fri, 03 Dec 2010 22:27:04 -0800, snipped-for-privacy@gmail.com wrote:

And it looked beautiful in the photo. Me like!

Agreed. Scale seems off, too, number size too large for my taste. I find that I prefer the horizontal style to the equatorial.

Large Roman numerals work, though. Brass is beautiful.

Smaller numbers are better.

Has that lovely "Made in Chiwan" look.
Is this a hobby or your retirement vocation, Mikey? You've sure made a passel of them thar thangs.
-- "Human nature itself is evermore an advocate for liberty. There is also in human nature a resentment of injury, and indignation against wrong. A love of truth and a veneration of virtue. These amiable passions, are the latent spark. If the people are capable of understanding, seeing and feeling the differences between true and false, right and wrong, virtue and vice, to what better principle can the friends of mankind apply than to the sense of this difference?" --John Adams
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On Sat, 04 Dec 2010 06:08:35 -0800, Larry Jaques
[...]

Thank you.
I have sold a few. Not enough to feed the family and very little recently for obvious reasons. Thus to describe it as anything other than a hobby would be overstating it.
It is interesting what people appreciate. Some of my best pieces remain unsold. The plastic crap was flying off the shelves until recently. When I go through my photos in a chronological order and look at some of the earlier stuff I cannot but ask "people actually paid for that?" I have got better since then in all areas including photographing the things but the sales are way down.
Maybe one of them tax cuts will trickle down to me...
Michael Koblic, Campbell River, BC
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On Sat, 04 Dec 2010 20:47:26 -0800, snipped-for-privacy@gmail.com wrote:

They don't sell as well in the rain, sleet, and snow, eh? My glare guards don't sell as well in the winter, either.

A hobby anticipating commercial sales, then. I developed the glare guard for an attorney client of mine who wanted to use her laptop at the park when she was watching over her little girl. (Yes, I gave her a raised eyebrow over that one, too.) I've sold over 100 of them so far, and they continue to be tank tough. Fun, but not as profitable as I'd imagined, and they're a chore to make properly. I went through the same challenges finding the right adhesive as you are having with the etching. Most adhesives lay on in lumps, and that telegraphs right through the ripstop nylon cover. <sigh> And would you look at the -price- they're getting now for 3m Super 77 spray adhesive! <thud>

Grok that.

Sorry, sir. You're in the wrong country for that. I believe they serve tax grabs at/to you up there, not cuts. But we'll not have any tax cuts while The Chosen One is in office, I'm sure. (No matter what he might or might not say.)
-- You can't wait for inspiration. You have to go after it with a club. --Jack London
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On Sun, 05 Dec 2010 06:13:13 -0800, Larry Jaques
[...]

My favorite subject, glues. Today I counted that I may use up to five different glues on a single dial.
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On Mon, 06 Dec 2010 17:34:55 -0800, snipped-for-privacy@gmail.com wrote:

You're a real stickler, are you? <groan>
Finding the proper adhesive turns the product from amateur to pro in seconds, doesn't it? What a difference they can make.
-- You can't wait for inspiration. You have to go after it with a club. --Jack London
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On Mon, 06 Dec 2010 19:26:32 -0800, Larry Jaques

Or it could just be an unholy sticky mess...Seriously, the best fun with glues is re-wiring fencing swords.
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On Tue, 07 Dec 2010 22:08:35 -0800, snipped-for-privacy@gmail.com wrote:

Yes, an unholy, sticky, BUMPY mess which later untacks and blisters up. Not good.

Reminds me of an old play by Uncle Will. "Epee or not to epee. That is the question."
-- You can't wait for inspiration. You have to go after it with a club. --Jack London
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snipped-for-privacy@gmail.com wrote in

I tried 'em all. I do all my re-wires with hot melt now. You need the right flavor, but it sticks well, is flexible, but easy to remove when the wire breaks.
Doug White
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wrote:

I find that different blades need different glues. I tend to use CA.
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On Dec 1, 11:13pm, snipped-for-privacy@gmail.com wrote:

snippage
I'd be more inclined to use sodium hydroxide with aluminum, you're going to run into problems with oxides even if you give the surface a good solid scrub with abrasive first. Lye was what we used to etch aluminum prior to anodyzing it, ran it at about 150 degrees F, removed residual oxides very well. Ferric chloride was what I used to use for copper circuit boards and brass name plates. The polymer in laser printer toner is a fair resist if you can get a good transfer. Once again, you've got oxides on the aluminum surface that tend to keep any bonding rather poor.
Alternative is to cut a vinyl mechanical mask and use an air eraser for small parts or a sandblaster for large parts to get the pattern you want. Certainly would be less hazardous as well as repeatable.
Stan
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