First Thoughts on Anodising

[Neil WyattModerator @neilwyatt]

It would feel fraudulent to write a 'how to anodise' posting following just a few day's experience!

But I have learned a few lessons, so rather than an incomplete or inexpert how-to, here are a few tips that might help others:

You are going to use a lot of nasty chemicals especially caustic soda and sulphuric acid. Stock up on latex/nitrile gloves, get goggles, old jeans (ideally ones that already have acid holes in). Make plenty of space and get things arranged in a logical manner.

Fairly dilute caustic soda cleans aluminium and strips failed anodising well, but it goes off rapidly with use. I found myself using fresh each time rather than mixing up a really strong solution.

Cleaning with dilute washing up liquid before and after the caustic bath is essential to remove any grease layer that will inhibit cleaning or anodising. If you touch the work after cleaning – clean it again or you WILL find a fingerprint in you anodising.

My sulphuric tank was at about 12-13%, this seems to work well and is below the 15% threshold where you need a licence to hold it.

I used a sealable 6-litre box for the acid that came with a plastic grid in the bottom, this helped make sure that the bottom of things anodised, but I found it helped to move objects around a few times during the process.

I sat this box in a large washing up bowl with an inch of sodium carbonate (washing soda) solution in the bottom to catch and neutralise any drips.

I had a second bath full of dilute washing soda to neutralise things as soon as they came out of the acid. I could then get them to a sink for rinsing before going into the dye.

Rinse between all solution changes.

The commercial dies I tried were excellent! They work best at about 50C so warm them up!

I tried scarlet Windsor and Newton ink for red, it was very poor.

Red Quink worked a bit better, but only made a weak pink.

Blue washable ink worked really well.

Sealing solution seems to work well, but they still recommend a steam/hot water sealing as a second step.

The final result may look uneven with brighter and duller patches. I found (after some experimentation) that gentle rubbing with a damp 'magic sponge' rapidly and easily gave an consistent satin finish without scratching.

Make sure your power supply is up to the job and keep an ammeter in circuit. If the amps get to high, fit a low-value power resistor in series (I used 0.5R for my largest piece to keep the current to 4A) Extend the anodising time for larger pieces, especially if you have to limit the current.

Finally, think safety at every stage.

[Neil WyattModerator @neilwyatt]

[I.M. OUTAHEREParticipant @i-m-outahere]

I think Ramon Wilson may have beaten you to it !

All good info there Neil ! I haven't had the need to anodise anything yet but that will probably change once i finish the hit 'n' miss engine i'm currently building , then a ME beam engine , a mastiff etc ,etc.

Eventually i want build a murrays engine but really bling it up , the frames made from polished then jeweled alloy so maybe some of the other fittings could be anodised .

Hopefully there will be more replies here so it becomes a nice long thread with plenty of info in it for us to reference later on if needed .

[I.M. OUTAHEREParticipant @i-m-outahere]

Btw congrats on the 14k posts that you will pass in the next 24 hrs !

[Neil WyattModerator @neilwyatt]

Posted by XD 351 on 07/09/2018 01:22:58:

Btw congrats on the 14k posts that you will pass in the next 24 hrs !

I can't miss the chance to thank you for that (and ring the bell!)

Neil

[JohnFParticipant @johnf59703]

Never done anodising but I do a fair bit of hot caustic blacking of steel components and where any corrosive chemicals are being used I would advise the use of a full face visor rather than goggles plus I always have a large bucket of clean fresh water close by with a suitable cloth in case of splashes or other accidents—touch wood not needed up to now but !!!

John

[VicParticipant @vic]

Posted by JohnF on 07/09/2018 10:08:05:

Never done anodising but I do a fair bit of hot caustic blacking of steel components and where any corrosive chemicals are being used I would advise the use of a full face visor rather than goggles plus I always have a large bucket of clean fresh water close by with a suitable cloth in case of splashes or other accidents—touch wood not needed up to now but !!!

John

Very wise John. Axminster tools sell inexpensive full face visors.

[BazyleParticipant @bazyle]

By 'commercial dyes' do you mean special anodising ones? If so where do you get them and are they available in less than a ton quantities which is often the problem with pro stuff. Do any of 'our' suppliers have them in sensible packs?

[VicParticipant @vic]

Posted by Bazyle on 07/09/2018 12:33:06:

By 'commercial dyes' do you mean special anodising ones? If so where do you get them and are they available in less than a ton quantities which is often the problem with pro stuff. Do any of 'our' suppliers have them in sensible packs?

Getting proper Anodising dyes in small quantities hasn’t been a problem for many years. Just do a google, this was the first hit I got.

**LINK**

[Ian S CParticipant @iansc]

I have not done any anodising (yet), but from what I'v read a good dye is the Dylon dyes normally used for fabric, it comes is little aluminium containers about 1 1/2" dia X 1/2" high. Lots of colours.

Ian S C

[Neil WyattModerator @neilwyatt]

I got my supplies of specialist chemicals from Gateros Plating.

http://www.gaterosplating.co.uk/anodising-main

Around four pages of datasheet with each one.

[Neil WyattModerator @neilwyatt]

Another thought… I made a point of getting 6082 for all the parts of my telescope as it is supposed to be good for anodising, strong and using one consistent material shoudl give more consistent colour.

I've just put the last component in the bath, but as it's quite small I strung a series of other small bits and pieces from around the workshop on the titanium wire. Only one of these was already anodised – a bit of door handle remodelled as a holder for a dial indicator, of unknown composition. It didn't appear to strip well in caustic soda well it will be interesting to see how it takes. Next an odd bit of bar, probably 6082, filed and machined into a quick change holder for the same indicator. Then the nut and washer from my lathe drawbar, made many, many years ago. Obviously not 6082 as it went black in the stripping bath! Obviously this allow is one of the ones where you are supposed to use a desmutting bath (nitric acid – more nasties!) so I just scrubbed them but they didn't come very clean, especially the knurl and the bore I coudln't get to with a kitchen scratchie*!

These last two seem to have gone very bright and clean in the sulphuric, so perhaps they will anodise OK.

I'll report back in an hour or two!

Neil

*AKA 'washing-up-diddy'

[Andrew TinsleyParticipant @andrewtinsley63637]

I have done anodising for years and it is pretty fool proof. If you want to give it a try, buy one of the kits that several companies sell. A friend used Ebay for his kit and he got excellent results first time.

Please note the Safety warnings that come with the kit and also in the above replies.

Dyes can be problematical, I have used Dylon initially but not all colours work. The Reds do and the Kingfisher Blue as well. Some of the greens don't work and it is said (not by me!) that the pores left by the anodising process are very small (true) and some of the large molecule dyes won't go into the pores (which I doubt).

You are probably better off buying the correct dyes for the anodising process. If you are going to use the anodised product on say a finned jacket for an IC engine. I believe there are dyes which don't degrade at higher temperatures. The Dylon reds last a long time but eventually go a sort of pink shade in IC application.

Andrew.

[MuzzerParticipant @muzzer]

Quite an interesting article from Misumi on anodising. Always been fascinated by the "sort of hexagonal" structure of the oxide cells that are formed. These are electrically insulating of course and can actually form a fairly effective insulation layer.

In a previous company, we found various instances where the primary insulator (typically Mylar film) on some mains equipment had been punctured by swarf or other particles but the anodisation layer had been able to withstand the test and / or operating voltage. Not something you should rely on and not something that would be approved but almost certainly prevented quite a few field failures.

Must try the process myself some time….

Murray

[john fletcher 1Participant @johnfletcher1]

I have a copy of an anodising article by Ramon Wilson in Model Engineer, I think it would be September 2012 as it was advertising the October Model Engineering exhibition of 2012.Also I have another copy of anodising, again from ME, this article is by Gerald Smith, not sure of the date,both detailed and very informative.John

[FatgadgiParticipant @fatgadgi]

Hi Neil ….. does Gateros sell sulphuric at 15% (it's not stated on their website so far as I can see) ? I've anodised for many years, so still have a supply of diluted, but it wont last for ever and I wasn't smart enough to stock up.

Cheers Will

[Neil WyattModerator @neilwyatt]

Posted by Will Bells on 07/09/2018 20:19:53:

Hi Neil ….. does Gateros sell sulphuric at 15% (it's not stated on their website so far as I can see) ? I've anodised for many years, so still have a supply of diluted, but it wont last for ever and I wasn't smart enough to stock up.

Cheers Will

I think they have assumed people will just buy battery acid from a motor factor, of course it's getting more complicated now.

£39 for a permit, it lasts three years but you need the faff of getting a countersignatory and two documents from a list where most people get electronic documents now…

Neil

[Neil WyattModerator @neilwyatt]

Posted by Neil Wyatt on 07/09/2018 20:30:48:

Posted by Will Bells on 07/09/2018 20:19:53:

Hi Neil ….. does Gateros sell sulphuric at 15% (it's not stated on their website so far as I can see) ? I've anodised for many years, so still have a supply of diluted, but it wont last for ever and I wasn't smart enough to stock up.

Cheers Will

I think they have assumed people will just buy battery acid from a motor factor, of course it's getting more complicated now.

£39 for a permit, it lasts three years but you need the faff of getting a countersignatory and two documents from a list where most people get electronic documents now…

Definitely a market for someone like Gateros to sell it diluted to 15%.

Neil

[Mark RandParticipant @markrand96270]

I'm in the process of starting to make a couple of 5 step poly-V pulleys for the milling machine out of aluminium. I suspect that hard anodising might help them to last better* . If I visit messrs Gateros plating's site and buy one of their kits, then mix the acid up a bit weaker and keep the temperature low and run the voltage up higher, can I do a DIY hard anodize? Current and voltage supply and control are not a problem, knowledge is…

*The original A section, 4 step, pulleys lasted less than 60 years. Albeit, a previous owner's apparent changing of the speeds with a crowbar when he lost the handle to loosen the belts hasn't helped.

[Clive HartlandParticipant @clivehartland94829]

I have never seen an anodised pulley? I think that it might be a bit OTT for a pulley. Further thoughts, that an iron pulley will have greater momentum than an Alu. one. Anodising is after all a protection method for weathering or handling or cosmetic?

[Neil WyattModerator @neilwyatt]

I think hard anodising may require a bit more sophistication for success. That said I'm sure it possible.

But also ordinary anodising will be fine for a pulley.

I'm thinking of anodising the pulley I made for my mill, but just as bling, not to make it work better

Neil

[Clive HartlandParticipant @clivehartland94829]

The anodising is graded as AA10, AA15, and AA25 denoting the depth and toughness, durability. ASA 25 for things like shop front surrounds. All done in the caustic bath and then anodised. A quick flash anosdising is not much use as it will wear away quite quickly. I have seen skirting boards 4 meters long being anodised for a building in London. some were rejeccted due to fading/change in colour over the lengths. Easily re-done, the colour, a bronze colour which was quite hard to keep the same through a batch.

[Swarf, Mostly!Participant @swarfmostly]

Re HARD anodising:

Many years ago I had visibility of a project that employed many aluminium alloy parts that were hard anodised. So, the following from memory:

It was found that hard anodised parts 'grow' by an amount that will prevent close fitting of parts but is not always easy to predict. It was also found that the hard anodising film is vulnerable at sharp corners and sharp edges. So sharp corners and edges had to be rounded.

Best regards,

Swarf, Mostly!

[Neil WyattModerator @neilwyatt]

I was boring an eyepiece adaptor out to take 1.25" eyepieces. When I got to just over 31.75mm a piece of 1 1/4" tube would just fit, but my collimator with a body made of the same tube, anodised, wouldn't. I was taking sub 0.01mm cuts to creep up on when it would just fit without force.

Of course now I've anodised the adaptor the collimator may not fit – but not important as it seem EPs are generally a few thou undersize while the 'sockets' are generally dead to size. Odd as usually shafts are to size and the hole adjusted to give the required fit.

Neil

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