Not tried anodising but it's amps that do the work in electrochemical processes. You only need enough volts to get current flowing, about two. The extra 10 to 12V volts will cause nothing but unwanted snap crackle and pop, tending to disturb the finish.

A resistive dropper will waste a lot of power, but easier than finding a 3V 10A psu. Try wiring a 12v car headlamp bulb in series with one of the DC connections, it will drop about 12V, probably OK because chargers run at about 14V. The DC from a car battery charger is pretty dirty – about 14vdc unsmoothed, I'm not sure if that matters. I'm assuming car battery chargers are as crude as in my youth; a modern one might be beautifully smoothed and too clever for anodising.

Worth a try, why not?

Dave

Never got round to trying it myself but do intend to do so eventually. I watched an awful lot of videos on the subject of homeshop anodising on Youtube and many of them use a 12vdc battery charger at both 6 and 10 amps or a very similar supply. Best try it on a test piece and see how it goes. Try what you have before lashing out money on something you do not need. Nothing ventured nothing gained.

regards

multi-amp 3.3V or 5V are available from many computer PSU’s – they generally cost less that ?5 at my local auction house – 12V high current (80A+) tend to be somewhat more expensive especially if they come with many 4 or 6pin graphics card interfaces as these are popular with bit-coin miners

You could try with a battery first. My book suggests 2 A and 10 V so it might be worth a try with a car or motorcycle battery, or even with a 9V battery

Edited By Gerard O’Toole on 15/01/2020 09:22:32

I had great results with a 12V 4A charger. I use a moving ammeter to keep an eye on current. It swings off the scale at first, but drops in less than a second.

The current self-regulates with the area of the piece, and if a bit low just keep it in longer. I always turn the part once.

For smaller parts keep the cathode further away.

I anodised most of this scope, the main tube is about 10" long, about 3" diameter so that's approaching 200 square inches inside and out.

Neil

Don't obsess about the voltage the things that matter are thorough stripping, cleanliness, good electrical contact between cathode (I use TI wire, cleaned with abrasive paper), professional dies and if you want to add another – more cleanliness.

Also, be careful, these are nasty chemicals.

Neil

Edited By Neil Wyatt on 15/01/2020 09:46:57

Nice job on the scope Neil.

I'm going to reveal a hidden gem here:

Get one of the Low voltage AC/DC power supples intended for use in schools like this one

https://www.ebay.co.uk/itm/POWER-SUPPLY-EJ0032-IRWIN-L-V-Variable-AC-8A-DC-5A/254479418781

or 8A one

https://www.ebay.co.uk/itm/POWER-SUPPLY-EJ32-IRWIN-L-V-Variable-8-Amp-AC-DC-volts/124032526494?

Search Irwin power supply. The also made one with stitched positions fron 2 to 12V

Griffin & George also made them.

Some are over-priced eg https://www.ebay.co.uk/itm/Variable-Power-Supply-Griffin-and-George-ltd-London/202874378189?

Some are absolute bargains like this https://www.ebay.co.uk/itm/GRIFFIN-AND-GEORGE-GRIFFIN-LT-VARIABLE-POWER-SUPPLY-/113986088771?

(No I didn't get that one but have an identical one).
These are unregulated and are much more suited to to plating, and running small motors than modern solid state digital units.

Don't forget that if you want to have sulfuric acid stronger than 15% you need an Explosives and Poisons Precursors licence in the UK

https://www.gov.uk/government/publications/licensing-for-home-users-of-explosives-precursors/licensing-for-home-users-of-poisons-and-explosive-precursors

Robert G8RPI.

Edited By Robert Atkinson 2 on 15/01/2020 15:58:10

Easily avoided by using sulphuric at just less than 15%, which works fine.

I don't want to overstate it, but my advice is based on practical experience, and before I started I took advice from Gateros Plating who make their living supporting hobbyist platers and anodisers.

I know the approach I use works from experience and gives good results,even if it isn't theoretically optimal.

You waste a lot of time worrying about exact voltages, but if you do that you should also be fretting about exact bath temperatures, electrolyte concentration, anode area, anodising time etc.

Transformers are good PSUs because they cope well with sudden, brief surges.

Bear in mind this is bucket chemistry, not precision engineering, plus the nature of anodising is that the area of the work helps determine the current. It's got more in common with cooking.

If you want perfectly identical loaves every time you need to control EVERY aspect of the process.

If you want a lovely artisanal loaf out of your wood-fired oven, just get it hot, shove it in and take it out when its cooked properly.

Yes, the ammeter confirms the output is un-smoothed. If the anodising results are iffy, I'd try sticking a capacitor across the output to see if it helps.

I think the actual ratio is A_rms/A_arith = 1.414 (approx 1.5 on the ammeter's scale)

1.414 is the square root of 2, and it defines the relationship between AC peak Volts and AC rms Volts in a sinusoidal waveform. Vrms = Vpeak / sqrt(2)

Following a waveform peaking and troughing 50 time a second stretches the imagination. It's often more meaningful to ignore reality and work with the average value instead. Various ways of calculating averages, but Root Mean Square is the most useful way of calculating the average value of a sine wave. It's like flattening out the wave by filling the troughs with the peaks.

Not sure having two scales on the ammeter is worth much beyond a general indication the charger is working. The meter used in chargers is only about ±25% accurate. On a Charger they indicate 'not working or finished', 'about right' and 'lots, maybe too much'. Useful, but not precise!

Dave