Where to get washing soda?

Hi all,
This week I was lucky enough to acquire a laboratory power supply. It
supplies 0-25 V DC at up to 15 A. I thought it would be ideal for doing
a bit of electrolytic de-rusting, but I can't find any washing soda.
I've tried all the likely stores such as Wilkinson. Does anyone know of
any chain stores which regularly stock it? Or any independent stores in
north Shropshire which stock it? I'm sure I've seen that "Arm & Hammer"
brand stuff for sale in the past.
Best wishes,
Chris
Reply to
Christopher Tidy
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Mine came from Tesco, but be careful with that power supply as it's totally OTT for the job, the recommended supply is a current source at no more than about 250mA. I use a NiCad charger set to less than this and it works fine. If you were to accidentally set your supply to 15A you'd get a lot of explosive gas generated very quickly...
Greg
Reply to
Greg
Admittedly I'm doing things on a smaller scale, about 15l of water in a plastic crate and objects no more than about 8 inches long, but 200mA has worked fine in a couple of days with little gas generation. Turning it up to around 400mA generates copious amounts of gas, to the point where you can smell it building up in the garage which is probably dangerous, and doesn't seem to speed things up so there really is no point. I would caution against using the voltage setting to control things, if you don't use the current limit then the current can vary wildly as you move the object around and gas production is unpredictable, at least in my experience.
Greg
Reply to
Greg
Thanks for all the suggestions. We have a Somerfield locally so I'll try there first, then go to Aldi or Tesco if they don't have it.
Opinion seems to vary as to what is a good current to use. Some people suggest very low currents (like you) and yet I found a post by Mark Rand from a year or two ago saying that he used 100 A for one job! I'm looking towards the larger end of the scale. We have a spare wheelie bin so I was thinking of using that to hold the electrolyte. Fortunately the power supply voltage is adjustable from 0-25 V, and it has both an ammeter and voltmeter on the control panel, so I should be able to keep things under control!
Best wishes,
Chris
Reply to
Christopher Tidy
Start low, such as 5 volts, and go up if needed. Electrolyte does not matter, just conductivity. Professionals use caustic lye. I use Liquid drain cleaner, about 1 cup per gallon works fine for me. Just never use any salt containing chlorine. With constant voltage and conductivity, the distance between the electodes controls the amps. So start with electrodes as far apart as possible and move closer if needed.
Reply to
bw
As there are always new people reading these threads, it's worth reiterating that you should not under any circumstances place aluminium or zinc based metals in a soda bath, let alone a caustic soda solution!
Why?
Because it will simply vanish into the solution leaving you nothing but a bare wire hook and a sinking feeling.
Reply to
Kim Siddorn
This guy seems ... thorough
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BugBear
Reply to
bugbear
Yes indeed, and recommends less than a quarter of an amp for a typical job.
All I can add is that in my experience there is no need for multiple anodes, just a single plate will suffice if you turn the job half way through.
Greg
Reply to
Greg
Now I've found some. I asked my mother where to get some and she said "I've got a packet in the cupboard which I've never used". Problem solved!
Best wishes,
Chris
Reply to
Christopher Tidy
Ah yes. As when that idiot Malcolm 'cleaned' the cylinder heads of Ogri's Vincent in the 'Bike' magazine cartoon strip ;-(
Gyppo
Reply to
J D Craggs

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