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  1. #1
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    Default Anodising- first attempt

    I had a crack at anodising today. I'm very happy with the result. It's a laborious process though and you wouldn't want to be doing only one part.

    The process I used:
    1. degrease with acetone.
    2. clean in ultrasonic cleaner.
    3. anodise for 2 hours in 10% sulphuric acid (by weight) at 30mA per square inch of surface area (2A for this part).
    4. neutralise in 60g/L bicarb soda solution.
    5. soak in Caswells Blue 4A anodising dye for 15 minutes.
    6. seal in near-boiling nickel acetate solution (7.5g/L) for 15 minutes.


    You have to spray rinse with deionised water between every step to avoid polluting the chemicals.
    I placed a small frozen water bottle in the anodising tank to keep the temp under 24C.
    The anodising step has to be done outside- the fumes are foul and corrosive.

    The part is a jumbo ice cube mould I made in a fit of boredom.

    Merry Christmas to y'all.
    Attached Images Attached Images
    Chris

  2. #2
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    Would you give us the details about the power supply you have? Output, cost and where it came from.
    Thanks
    Pete

  3. #3
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    Certainly. 30V, 5A with constant current function. I set it for 2A and the current was rock solid as the voltage rose from 5V to 8.5V over the 2 hours. I was very impressed with it. Here's the one I bought, but there are dozens of eBay sellers offering the same unit.

    https://www.ebay.com.au/itm/DC-Power...72.m2749.l2649
    Chris

  4. #4
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    Hi Chris,

    Thanks for posting this. For years I have wanted to have a go at the process but I never found a simple straightforward recipe. Like most things there are numerous anodising recipes, some vaguer than others, some overly complicated. I imagine there is a bit more to yours than just the steps you outline!

    Not long ago I purchased ( with BobL's guidance ) a 10 amp 30V DC variable power supply on eBay with the intention of possibly using it for electrolysis, plating and anodising.

    The chemicals are probably a bit trickier to obtain than by just hitting the buy it now button though I have found some nickel acetate in Poland - https://www.ebay.com.au/itm/Nickel-I...YdEc:rk:3:pf:0

    Searching online for suppliers of sulphuric acid led me to an overclocker's forum where there was a discussion regarding sources of sulphuric for anodising. One bloke's comment was "I grabbed a 1lt bottle of 460g/l sulfuric acid at battery world. It was only 8-9 dollars. " The price would have undoubtedly increased because the discussion took place in 2010.

    Where have you obtained your chemicals?

    All the best for Christmas and the New Year
    Bob.





  5. #5
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by Anorak Bob View Post
    Searching online for suppliers of sulphuric acid led me to an overclocker's forum where there was a discussion regarding sources of sulphuric for anodising. One bloke's comment was "I grabbed a 1lt bottle of 460g/l sulfuric acid at battery world. It was only 8-9 dollars. " The price would have undoubtedly increased because the discussion took place in 2010.
    Battery world or any other battery place I know have not sold the sulphuric acid separately for a number of years - you have to purchase a battery along with the acid.

  6. #6
    BobL is offline Member: Blue and white apron brigade
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    Looks great Jack, i'm really interested in this but also want to avoid using sulphuric as I already have so much other nasty stuff around my shed as it is.

    Did a bit of a hunt around for anodising recipes and found that NaHS04 (Sodium bisulphate or bisulphate) can be used in place of Sulphuric acid.

    See Anodizing and dyeing aluminum without battery acid... - Observations

    He uses RIT cloth dyes and no nickel acetate.

    NaHS04 readily available as a pool chemical afor about $10/kg

    It's still going to stink and make lots of hydrogen on large pieces - ie ventilation required.

  7. #7
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    Quote Originally Posted by Anorak Bob View Post
    Where have you obtained your chemicals?

    All the best for Christmas and the New Year

    Bob,
    I bought the dyes, nickel acetate and some titanium wire from Caswell's USA and picked it up when I was over there. It was cheap, so I bought 4 colours. If I was buying from Caswell's in Oz I would probably just buy black and add other colours to the collection as required.

    I managed to find 98% sulphuric acid at an industrial cleaning supply company near me for $20 per litre. 1L makes 18L of 10% by weight solution (1L of 98% H2SO4 weighs 1.84kg). You can reuse the solution many times.

    This place in Perth has 33% H2SO4 in a 5L container. It would be a lot safer to handle than 98%. https://www.westchem.com.au/products/sulphuric-acid-33

    My research indicates that clothing dyes like RIT can give disappointing results. Given the setup and time involved, I don't reckon it's worth risking a poor result to save a few dollars on the dye. A 120mL bottle of Caswell's dye makes 8L of dye bath. You don't have to make it all up at once and the bath will apparently last years if you neutralise and rinse the part before dyeing.

    You can seal an anodised part by simply boiling it in deionised water for 15 minutes, but if the part has been dyed this can leach the colour out of the pores before they seal. The nickel acetate prevents this. Again the bath can be used many times. 100g will make 13L.

    The Caswell Anodising Manual is very comprehensive, but a little bit messy. There are numbers buried all over the place. I have made up a table which condenses all the numbers from the manual into a ready reckoner. I'll tidy it up and post it later.

    Merry Christmas to you too.
    Chris

  8. #8
    BobL is offline Member: Blue and white apron brigade
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    Thanks for the details on the chemicals especially the dyes.

    I really want to avoid storing any more concentrated chemicals as liquids around my shed as I already have way too many in liquid form and that's why I am using solid salts whenever I can. It's not just the concentrated liquid chemicals but all the containers/baths and chambers full of working liquids that need to be stored.

    I'm thinking of building a small external storage cupboard where I can store some of this stuff but have yet to find a location for it.

  9. #9
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    Quote Originally Posted by BobL View Post
    I really want to avoid storing any more concentrated chemicals as liquids around my shed as I already have way too many in liquid form and that's why I am using solid salts whenever I can.
    I don't blame you. The 98% sulphuric acid is scary stuff. I added 350mL to 6L of water and the heat generated was incredible. The solution was still warm a couple of hours later. 33% would be a lot safer.
    Chris

  10. #10
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    Here's the table I made up. Very handy in the shed when doing the process.

    And here's a link to the 720 Rule calculator. Enter desired thickness in mils from my table. I used 0.7 mils and a current density of 4.5A/sqft. The time is the number you need. The peak voltage reading is a function of a number of variables. I didn't get anywhere near the predicted peak voltage at the end of the time period.

    https://www.caswellplating.com/720.html
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    Chris

  11. #11
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by jack620 View Post
    I don't blame you. The 98% sulphuric acid is scary stuff. I added 350mL to 6L of water and the heat generated was incredible. The solution was still warm a couple of hours later. 33% would be a lot safer.
    If anyone else decides to try this, best to start the water swirling around the container and add small shots eg 30mL of acid, at a time and stir it in before adding the next shot. Starting with colder water can also help.
    Also it's acid into the water and not VV.

  12. #12
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    Hi Chris, this is interesting to me but i think that i will stick to rattle cans as that is about as good as it gets around here

    So woch ya makin' ? Is this for the titanium pens ?

    shed

  13. #13
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    Hi John,
    I hope you had a Merry Christmas.

    I don't really have anything specific in mind. It's just something I've always wanted to try. I have a few home-made aluminium lathe attachments which don't actually need to be anodised, but what the hell?

    This method is not for the pens. Anodising titanium uses a different method. No dye is involved. The colour comes from the thickness of the oxide on the surface of the Ti. This is directly proportional to the voltage applied and happens almost instantly. This video is a bit slow, but demonstrates the method well. https://www.youtube.com/watch?v=IR90vWS16Is&t=314s

    I prefer heat colouring titanium. The colour is not as uniform and the result is less predictable, but gives a nicer look I think. The pen making is on hold while I wait for this to arrive:

    https://www.banggood.com/ER11-Chuck-...r_warehouse=CN

    I will use it to make a milling tool for the lathe so I can mill 3mm wide x 12mm long slots in Ti tube for some bolt-action pens. Solid carbide end mills and mist cooling should work OK.

    I also ordered a 500mm long piece of 11mm diameter Damasteel to make the tips of the pens. Parallell Layers™ - Damasteel®
    Chris

  14. #14
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    Chris i will be interested to hear how that spindle motor performs, I was surprised to see that the speed is controlled by the voltage.
    I think that this will be useful for a number of machining tasks, so if it lacks power at lower revs do you think that you might be able to get more torque with a pulse width modulator?
    cheers, shed

  15. #15
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    Default Anodising- first attempt

    John, I will post my findings here. I'm not aware of how the controller works. Are you sure it's not PWM?

    I got the idea for this from a Steve Jordan video. It seems to maintain revs under load pretty well.

    https://www.youtube.com/watch?v=ouGqR70ggNE
    Chris

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