Or rather, at the Hackerspace.
I’ve been interesting in anodising our own parts for about 5 years, idly, but lately i’ve started seriously looking into what it would take to make it happen. The answer is that its a bit tricky but not insurmountable.
The process, in simplest terms, seems to be:
- Start with a part that is as polished as possible, all marks will show.
- Clean in detergent and distilled water
- Soak in caustic soda solution to clean the surface of impurities
- Clean in distilled water
- Soak in nitric acid solution to desmut (remove surface alloy impurities)
- Clean in distilled water (separate bucket each time)
- Hang in sulphuric acid bath by the anode wire. Any covered surfaces will not anodise so pref jam the wire into a bolt hole.
- Apply power. Try to keep the bath at 20ºc for Type II, or 4ºc for Type III
- Remove from bath, clean in distilled water
- Soak in warm (<50c) concentrated dye solution. (use distilled water)
- Boil the part in distilled water for 30min to seal.
So I think theres a 2 step process to building capabilities to do this stuff. one is to just manage to do crappy anodising with a basic setup, and then two is to gain control over the variables. The variables are:
- cathode size (make the cathode mount so it can be raised/lowered in the bath)
- power in the system. ability to limit/regulate voltage and amperage
- temperature of the system. ie, a bucket of ice (dry?), a pump, teflon tubing and sensors that can withstand the acid bath. Also, a way to circulate the water that can withstand the acid bath.
So, heres a bit of a dump of my current research.
- High wattage power supply
- 1 piece of lead flat bar for a cathode
- 8 HDPE containers, preferably square, 5L seems a good size at a guess, maybe 10L. Borosilicate Glass would be better but that sounds even harder to source.
- A sheet of glass to work on. We’d probably make a table specific to this kind of use.
- Utilising the fume hood is probably an extremely good idea.
- The usual assortment of wires, switches etc.
- A hot plate or immersion heater
- 2 pots of any kind for the dying and sealing stages
- Appropriate PPE.
- Gloves (maybe even gloves for each stage to prevent cross contamination). I’ve not sourced gloves that are rated for this sort of thing yet.
- Eye protection (acid in eye sad times)
- Respirator for the lacking of acid fumes in lungs.
- Probably some kind of apron or overalls.
Stage Two Materials:
- Some kind of high amperage voltage stepdown / amperage stepdown / controller / meter etc.
- Press fit tube fittings
- PTFE or FEP tubing
- An esky
- A pump
- Thermocouples that have been potted in something acid resistant.
- Maybe some kind of PID control I guess. Human flicking a switch might be fine.
- A way of circulating the bath, I think an epoxy coated paint mixer would do ok, or we could make one from hdpe if it can’t hack it. A pump is out of the question, mag drive pumps for acid use are $$$$.
- Detergent (any) for stage 1 cleaning
- Distilled water for cleaning between every stage
- Caustic Soda or stage 2 cleaning [Alternative]
- Nitric Acid for stage 3 cleaning (desmut)
- Sulphuric Acid for the anodysing process itself
- Bicarbonate of Soda for neutralising acids / general safety
- Dyes (experimentation to be done here)
It’s of a pretty manageable cost, the only real pain in the ass is the large quantities of demineralised water that you chew through. The acid solutions seem to be reutilise for long periods.
We would need a real solution for the storage of dangerous goods. You can buy proper big metal cabinets for this sort of thing, and they do pop up on grays online semi frequently for cheap but they’re hard to shift. I’m thinking we could probably make our own but thats a high material cost (they’re typically a few mm of steel epoxy coated). However, this would be good for a lot more than just these consumables obviously. PCB etching chems, some of the naster stuff that gets used in the metal shop (deseizing solutions for instance).
We should also have a solid plan for the storage of both the acid concentrate and the solution, ie if it needs to be decanted back into a glass sealed container and if so, how to do such a thing safely.
Thankfully, the acid solutions seem to get fairly long lifespans of use. I’ve started the process of talking to JJ Richards (playing phone tag atm) to see what it costs for low level infrequent hazardous materials disposal. Very low levels of very dilute acids can be poured down the sink but I think we’re at a level where that cant be done.
The nice thing if that becomes something we do, is that that service also handles things like collecting motor oil and other similar things we currently struggle to dispose of.
Inductions / Documentation.
I plan to document the shit of it, but I think this is always going to be a highly restricted activity at the space rather than something anyone can just have a crack at. We might end up doing anodising days or something. We will just have to see as we go.
Well, I kind of need help to source stuff so that would be greatly appreciated. If you can find a source for something not linked above, or you can find a better source, please pipe up.
I would love some help solving the semi difficult problems, like the storage issues.
I would also like expressions of interest from people who are willing to pitch into this project, either with time and or money.