[Swansea Hackspace] Anodising

[Andy Davies]

Hi Andrew


Many thanks for getting back to me.


Which Ebay supplier do you use please?


Cheers


Andy

________________________________
From: Hackspace <hackspace-bounces at swansea.hackspace.org.uk> on behalf of Andy Rush <andymrush at live.co.uk>
Sent: 29 April 2020 15:09:37
To: Swansea Hackspace
Subject: Re: [Swansea Hackspace] Anodising

Hi, Andy

Sorry for the delay, I meant to answer, but got distracted.

Not going to lie, I've never really tried getting a matt result, I always usually aim for a gloss finish. I recall reading somewhere that the difference in finish could be achieved with the same dyes, but with different surface preparation, or light etching/sandblasting/tumbling after anodising. I'm afraid you'll have to do your own research there.

Cheers

Andrew

________________________________
From: Hackspace <hackspace-bounces at swansea.hackspace.org.uk> on behalf of Andy Davies <andy at andydavies.info>
Sent: 25 April 2020 13:26
To: Swansea Hackspace <hackspace at swansea.hackspace.org.uk>
Subject: Re: [Swansea Hackspace] Anodising


Hi Andrew


That is brilliant! Many thanks for taking the time to do this.


Do you have an Ebay link for matt black anodising dye or is there just black available?


Cheers


Andy



________________________________
From: Hackspace <hackspace-bounces at swansea.hackspace.org.uk> on behalf of Andy Rush <andymrush at live.co.uk>
Sent: 24 April 2020 16:48:18
To: Swansea Hackspace
Subject: Re: [Swansea Hackspace] Anodising

Hi, Andy

For the sake of my sanity, please call me Andrew, otherwise I'm going to to feel like I'm talking to myself.

Okay then. Seeing as we're on the Hackspace Mailing List, this email thread is probably going to double as the Anodising Tutorial Class that I've been meaning to do in the space for years, but couldn't quite figure out the logistics of. There's a 1.5 hour wait, irritating chemicals, some mild fumes, boiling water and some jury rigged electronics involved. I couldn't quite figure how to get that past risk assessment without giving Tom a cluster migraine. Anyone who wishes to learn anodising from the Advanced Amateur, listen up now. maybe save this mail somewhere.

At the end of this email, I'll link to a video tutorial a friend of mine (Darth Chasm, an excellent sabersmith and the man who taught me how to anodise in the first place) made, covering the whole process of anodising saber parts. it should hopefully clear up any points where I wasn't too clear on.

Before I get started: typing aluminium out every time is tiresome. I'm calling it Alum from here on. Also, some of the calculations will be done in Imperial units. this is because Americans have lead the way on anodising, so their calculators only work in Freedom units. Yeah, I'm not a massive fan of it, but it gets the job done.

So, the alum anodising process involves running a constant DC Current through a piece of alum in a chemical bath to grow (as I understand it, I'm still a little fuzzy on the science) a porous, ceramic-like, alum oxide layer on the surface of the alum. That porous layer can then be dyed (this is optional) and must be sealed, otherwise the anodised layer will just rub off. Aside from adding colour to alum, anodised Alum is also more weather resistant than raw alum, and the anodised layer is non-conductive. This is the main reason why alum gets anodised, as raw alum is a very good conductor.

The process can be reversed to strip off an anodised layer, either because the anodising wasn't good enough, the dye faded over time (we're talking decades) or because you want a different colour or to try powder coating (it's one or the other, you can't have anodised alum and powder coated alum at the same time). I'll cover that at the end.

one word of warning: traditionally, anodising is done with a dilute Sulphuric acid bath. That stuff is vile. I use an alternative chemical bath using Sodium Bisulphate as the main chemical. This is significantly safer for a hobbyist setup, but produces results that are "inferior" to the professional grade stuff. By that, I mean that when done properly, it will retain coloured dyes as well as the "real" stuff, as well as be electrically non conductive, but the thickness of the anodised layer will be inconsistent by a few fractions of a thousandths of an inch, which is fine for most hobbyist applications, but generally considered unsuitable/inferior by professional standards, or for engineering requirements.

Equipment you will need:

 - A DC power supply, capable of providing 30V at 5A. I personally use a relatively cheap DPS5005 from Amazon, powered by a 20V 2A laptop power brick. (See Jury Rigged electronics, above)

 - A plastic or glass container (NO METAL) big enough to completely submerge your work piece into (I've been using Wilko tupperware)

 - Distilled or Deionised water, at least 3L. it must be pure. Whatever you do, DO NOT use the fragrant deionised water they sell for ironing clothes. The water must be pure.

 - Sodium Bisulphate. Also sold as Sodium Hydrogen Sulphate. this is available on Ebay and Amazon, as a PH reducing agent for pools and spas. some of my American sabersmiths use a branded product called Spa Down. I suggest buying a 1KG tub.

 - Anodising dyes. these can be purchased through a specialist (Caswell plating), or Ebay. I have purchased from both, and honestly, the results were just as good with the cheap (£13/100g) Ebay dyes as they were with the *highly* expensive (£50/4oz bottle) Caswell dyes. It has been said on the internet that fabric dyes and food dyes also work, but after some experimentation, I've yet to find a brand (of either) that works.

 - some raw aluminium plates. The plates will serve as your bath's Cathode, and should have a surface area equal to, or greater than, that of your workpiece. they should ideally be of a similar grade alloy to your work piece.

 - Titanium wire. the titanium wire can be safely used to connect your work piece to  your power supply. Titanium can be used because it won't react with the bath at all, whereas copper would. I don't use this, myself, as my sabers have threaded holes in them, which I normally connect with a length of aluminium rod with a thread cut into one end. Titanium wire is used with great results by my fellow sabersmiths, and by the professionals, so I know it works.

 - Some regular wire and alligator clips to connect the cathodes to the Power supply

 - two pots/pans, preferably with lids, that your work piece can fit inside of, and will never be used for food again

 - A heat source capable of boiling water. If you're not willing to use your kitchen hobs, a camping gas hob or hot plate will do.

 - A thermometer that can be dipped in water, and won't be used for food.

 - wet and dry sandpapers in 400, 600, 800, 1K, 1.5K, 2K grits

 - fine and corse scotch brite pads

 - Fairy Liquid dish soap. Has to be Fairy Liquid, due to its higher lye concentration.

 - an old toothbrush

 - nitrile or vinyl gloves. Never latex, as the powdering agents on latex gloves can pollute the bath

 - eye protection. Sodium Bisulphate shouldn't damage your peepers, but it's good practise just in case.

 - a face mask is optional, as this process does release a small amount of hydrogen fumes. It's best to do this in a well ventilated area.

 - Scales. an electric kitchen scale will do fine, but maybe wrap it in foil or clingfilm if you want to use it in the kitchen again afterwards

 - Other things that come in handy: popsicle sticks, electric tape, plastic-coated garden bailing wire (must be plastic coated) a set of cheap and disposable helping hands, cheal and disposable needle nose pliers.

Step 1: Preparation

The Anodising Bath:

First, we'll prepare the anodising bath. Gloves and eye protection on! From experience, I've found that a 20-30% concentrated solution works best. I usually add 300g of sodium bisulphate to 1L of distilled water, but you may need more or less depending on the size of your work piece. Always add the Sodium Bisulphate to the water, never the other way around. you'll have to stir it for about 5-10 minutes until the crystals fully dissolved, and the water returns to being clear. once mixed, this anodising bath will last for some time. I've found that the quality of the anodising drops after either around 15 anodises, or 6 months in storage unused, whichever comes first.

>From here on out, threat this fluid carefully. think of it as boiling water. Do not spill it, slosh it, or put any exposed skin into it. Sodium Bisulphate is an irritant. if you have any open wounds/cuts/scratches and you get some fluid in them, they will itch like hell for a few hours. This is still better than what dilute Sulphiric Acid would do to you, though.

Important note: Once the anodising fluid is mixed, do not allow any metals other than Aluminium or the titanium wire into the bath. doing so will lead to impurities that will spoil your anodising.

After your anodising fluid is mixed, you can insert the Cathode plates into the bath. preferably, do not fully submerge them, so that you can connect the non-submerged parts to the power supply via wire+alligator clips. if you're using a tupperware container, I suggest bending the aluminium plates around the sides and top of the container. The cathodes should not make direct contact with the workpiece while anodising.

Put the bath aside for now. cover it with something when not in use if it doesn't have a lid.

Dye:

Mixing the dye is quite simple. take dye, mix with distilled water. the more dye you use, the deeper your colour will be. I tend to use powdered dyes from Ebay, and 1L deionised water bottles from Wilko's auto section, so for the most part I just open a bottle, pour the dye in, put the cap on and shake vigorously for a few minutes. Leave rest, then shake again before usage. Gloves are optional for this step, more for stain prevention than anything.

The work piece:

There are two steps involved here: measuring and surface prep.

Measuring:

So, first, we will need accurate measurements of your workpiece. This is because the total surface area of your piece is a key factor in working out the amount of constant current that we'll need to use during the process. once we have a surface area, we'll be using this online calculator http://www.ndhsubmersiblescience.com/ano/720rule.html to work out the current. Now, this is where things get Imperial. as you can see, the calculator works only in square inches and feet. unfortunately, all the Rule 720 calculators on the internet only work in Imperial units. I've found it just easier to make your surface area measurements in Imperial directly, rather than Metric and convert.

Now, I mostly anodise tubes and rectangles, so the calculations are relatively easy. I'm not great with numbers, so I just google for a surface area calculator that matches the shape I need, input my numbers in Inches, then repeat in another calculator to make sure the numbers match. it's lazy, but it works. the surface areas tend to have a lot of decimal places, so I round them up a bit just for safety (better over than under.) a hypothetical piece with an area of 25.750493" squared is better off being 25.8" squared.

Once you've worked out your total surface area, input it into the calculator. the only other variable you'll need to change is the Thickness setting. Now, Sodium Bisulphate anodising can't really guarantee accurate thickness, so all that that really does is work out how long you'll need to leave your piece in the bath.a thickness of 0.75 will always give you 90 minutes, and I've found that's a good length of time.

so, let's say your workpiece as a total surface area of 25.8" squared, and a thickness of 0.75 thousandths of an inch. the Rule 720 Calculator gives us a constant current of 1.08A for 90 minutes. save that for later, we'll get back to it.

Surface Prep:

This is the arduous, pain in the arse section. Sorry, there's no way around it.

Now, you may recall from school science classes that Aluminium is actually more reactive than Iron. but whereas iron rusts, aluminium is so reactive it forms an oxide layer with the oxygen in the air that protects it from rusting. Well, the good news is that when anodising, we're actually exploiting that oxide layer. the bad news is that we have to remove the existing oxide layer for an ideal finish.

yes, this is where the wet sanding paper comes into it. you will now have to wet sand your workpiece. immerse your sandpapers in a bowl of water with a little fairy liquid for five minutes. Why Fairy Liquid? well, apparently, Fairy have more lye in their dish soap than most other brands, and this helps act as an etching agent to help rough up and thoroughly de-grease the surface. I have been told (but can't confirm) that machine shops in the USA that specialise in anodising have been known to import Fairly Liquid specifically for this purpose.

You will also want another bowl of water on hand to store your work piece in, in between sandings. the theory there is that if the alum is in water, if can't form an oxide layer with the air. again, I have no way of proving that that works, it's just a widely held belief. I can't see that it harms the job, so I do it.

Anyway, now it's time to sand your workpiece. Wet the piece, then apply a little Fairy, then sand it in a circular motion with 400 grit. use a light touch, as 400 grit can still take off material if you force it. once you've completed a sanding, wash the soap off completely under running water, return your piece to its water bowl, and prepare the next grit up (600) repeat, going up through the grits, until you've reached 2K. you could go up to 3.6K, but I find that that's just overkill.

Once you've gone through the sandpapers, break out the coarse and Fine Scotch Brite pads, and repeat the process. water, soap, scrub, rinse, repeat with fine Scotch brite, rince, and place in water.

Now, ideally, you should do this in gloves, but I've found that the sandpapers tend to tear through them with ease, so I go without. for a final step before I anodise, I put on some gloves, apply a little soap, and scrub the piece with an old toothbrush, then rinse and return it to the water bowl.

Whatever you do, do not use steel wool, as fine fragments of steel wool can get caught in scratches in the aluminium. when they're placed in the bath, they'll turn into rust, which will damage the purity of the bath at best, and at worse cause orange splotches of absorbed rust on your workpiece.

Congratulations, you're now ready to anodise!

Step 2: Anodising

This is a very easy step. Your bath is ready, your piece is ready, now it's time to introduce A and B to VDC. the tricky bit here is making sure that you have a good electrical contact. you might have guessed from the name, but Anodising involves connecting your workpiece up to the Anode. this is where the titanium wire comes in. you will have to find a way of attaching your wire to your workpiece, preferably at multiple places, and in a location that won't be seen. This is because, as previously stated, when aluminium is anodised, it stops conducting electricity. therefore, we need multiple points of contact. the hidden location is simply because the parts that will be in contact with the wire won't anodise, so it won't take up any dye and will look splotchy. Ideally, you should do this under water, and while wearing gloves. this time because if the oils from your skin remain on the surface of the alum while anodising, you will get fingerprint-shaped messes on your anodise.

As I said above, my saber pieces tend to have threaded holes in them, so for electrical contact, I cut a thread into a short length of aluminium rod and thread that into a hole and connect my Anode to that. I don't use titanium wire, so I only have limited knowledge of how to apply it. from what I understand, it's quite springy, so if your workpiece has a recess that you could jam the wire into and use its springiness to clamp against the sides, do that. I know that the professionals machine clamps out of either alum or titanium, but that's beyond my capabilities as a hobbyist. Whatever you do, check conductivity with a multimeter before you put your piece in the bath

Once you've worked out how to connect your piece, it's time to place it in the bath. GLOVES AND EYE PROTECTION DEFINITELY ON. There's a couple of things to make sure of:
 1: make sure your piece is fully sumberged, preferably at least 1cm under the surface. this is where plastic-coated garden bailing wire comes in really handy, as you can just make a support bed inside the bath, or hanging from the sides of your container, that will support your piece at the ideal height.
 2: make sure your piece does not make contact with either the container, or the Cathode plates. Any alum that makes contact with the bed won't anodise properly, and any contact with the cathode will cause a short and royally screw up the anodising job.

Once you have your piece in the bath, and the cathodes in the bath, it's time to bring the power supply into it. be careful here. don't connect the workpiece to the power, as once VDC is going through, your piece will start anodising. you will want to set your power supply to the Amperage we calculated earlier (1.08A for 90 minutes.) If your PSU has a Constant Current setting, turn it on. if not, set the amperage to 1.08A and the voltage to full. once the power supply reaches 1.08A, it should regulate the voltage to keep it at 1.08A. with that set, it's time to connect your workpiece. this is where lengths of wire and alligator clips come in handy. Connect the negative lead to the Cathode plates, and the positive lead to the work piece, being careful that no connecting metals other than aluminium and titanium are in the bath. no submerged alligator clips, no submerged copper wire.

And then turn the power on. If you look at your workpiece, you should see bubbles forming on the surface. Keep an eye on your power supply. Mine tends to start with a large voltage spike, as the voltage goes up fast to hit the correct amperage, then when that's reached, the voltage will start slowly falling. And now, we play the the waiting game. for 90 minutes. Put a timer on. watch a short movie or something. it's all downhill from here.


Step 3: Dye

Preparing the Dye

You may wish to put a second timer on for ten minutes before the anodising is due. Most anodising dyes have to be heated up before they can be used. This is where the pots, hob/hot plate/thermometer come in handy. So, put a pot on the hob, pour in the anodising dye you prepared earlier, and begin to heat it up. the ideal temperature you're looking for is around 65C to 70C.  WHATEVER YOU DO, DO NOT ALLOW THE DYE TO BOIL. The issue here is that boiling water is key to sealing, the final step of the anodising process. if the dye is too hot, the heat will seal the anodised layer BEFORE the porous layer can suck up enough dye. Temperature control is key, so use a thermometer. once your dye has reached 65-70C turn the heat off and put a lid on it.

90 Minutes later

So, your second timer has gone, and the anodising is ready to be dyed. if your dye isn't hot enough yet, don't worry, you can leave the piece in the bath for a little longer. what you must not do is turn the power supply off. Remember, the anodised layer is very porous. If the power is cut, if will start sucking up the anodising fluid into its pores before it sucks up the dye, and you'll get a blemished finish. when you're ready, just yank the workpiece out of the bath by the titanium wire lead, drain any fluid back into the anodising bath, and turn the power supply off. being careful not to drop your workpiece, plunge it into the dye bath.

As with the anodising bath, the ideal situation is to have the piece submerged about 1cm under the surface, and not in contact with the pot itself, as this will leave areas were the dye won't be able to reach the anodised layers, and therefore yet another cause of a splotchy finish. as last time, plastic coated bailing wire helps, and a set of helping hands can be used to hold the titanium wire lead at the proper height. put the lid back on, and leave it in for 20 minutes. You can go longer if you wish, but I've found that the colour uptake doesn't get much better after that. Your mileage may vary, of course.

Step 4: Sealing

So, your piece should hopefully be dyed. now comes the final step, sealing. This is done simply by placing your workpiece in plain old thermally agitated dihydrogen monoxide.

Yeah, you boil it in water. So, in your second pot, boil some water. Maybe start around the same time as your dye bath. just don't get the two mixed up. A kettle may come in handy here. So, once dyed, extract your piece from the dye bath. you can simply drop your dyed piece directly into boiling water and simmer for 20 minutes (keep an eye on the pot to make sure it doesn't boil dry,) but I've found that the surface finish can be greatly improved by steam sealing. With the aid of a pair of cheap, disposable, long needle nose pliers (they'll get rusty after a few steams), you can hold your work piece above the boiling water, in the steam that's boiling off from it, for a minute or two. this will start the sealing process, so that when the piece is plunged in the boiling water, the pores are partly closed and the dye within doesn't get a chance to leak out.

After 20 minutes or so, drain the boiling water, and let your piece air cool. aluminium cools fast, so in five minutes or so you should be done. Extract the titanium wire lead, and you're done. the anodised layer takes a polish nicely, so if you've got some Mother's Mag, that should get it nice and glossy.

There. I hope that's comprehensive enough for most people to understand without visual aids/a demonstration. If not, here is the promised video from M'colleague and Anodising Sensei, Darth Chasm (No, I don't know his real name, either) https://youtu.be/PFjocxJERA0

Step 5: Stripping

Something went wrong. The result was splotchy. or, you just don't like it in day-glo orange and want it in purple? Okay then. time to strip. For this, you will need: a plastic container, some water (tap will do fine here), Gloves, mask, eye protection, ventilation and some sodium hydroxide, AKA lye, AKA drain de-clogging powder.

fill your plastic container with enough tap water to submerge your piece. then put on ALL THE PPE. pour in some lye. I don't usually measure a set amount, as I've found that this stuff is so potent that about 50-100g will eventually eat away an anodised layer. let's say, about 150g/litre. stir it in slowly and carefully for a few minutes. as it mixes, the lye solution will get quite hot. I usually find that's the right time to stop stirring.

tie your workpiece to some string, or something. you really don't want to go fishing around for it in there. then, carefully put it into the lye. the reaction should be quite rapid. there will be some fumes and a lot of bubbling. For god's sake, don't be daft, don't breath the fumes. after 30 seconds, you'll want to extract your piece, and carefully run it under a tap for a minute or so to clean the lye off and inspect the progress of the stripping. if the anodised layer is still holding on, return it to the lye bath for another 30 seconds, then rinse under a tap. repeat until the anodising layer is completely removed.

Now there are a couple of caveats that I haven't covered (compatibility of aluminium alloys, for one) but this should be enough for a general purpose how to. I hope this helps.

Cheers

Lightsaber Andrew

________________________________
From: Hackspace <hackspace-bounces at swansea.hackspace.org.uk> on behalf of Andy Davies <andy at andydavies.info>
Sent: 24 April 2020 00:39
To: Swansea Hackspace <hackspace at swansea.hackspace.org.uk>
Subject: Re: [Swansea Hackspace] Anodising


Hi Andy


I'd like to see if I can do it myself if possible.


So, some pointers on how to go about this would be great. Where to buy materials and equipment etc. Technique?


I'll be doing small aluminium plates for photography.


Many thanks


Andy

________________________________
From: Hackspace <hackspace-bounces at swansea.hackspace.org.uk> on behalf of Andy Rush <andymrush at live.co.uk>
Sent: 23 April 2020 19:20:15
To: Swansea Hackspace
Subject: Re: [Swansea Hackspace] Anodising

Lightsaber making weirdo present!

I can certainly help. What are you looking for? tips and tutorials, or someone to do it for you? what sort of smallish parts are we talking about?

Cheers

 Lightsaber Andy

________________________________
From: Hackspace <hackspace-bounces at swansea.hackspace.org.uk> on behalf of Andy Davies <andy at andydavies.info>
Sent: 23 April 2020 17:43
To: hackspace at swansea.hackspace.org.uk <hackspace at swansea.hackspace.org.uk>
Subject: [Swansea Hackspace] Anodising


Hi


I can remember meeting on of the members who made light sabers and could offer some advice on how to get started with anodisng.


I just need to coat some smallish aluminium parts in matt black.


Cheers


Andy
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