DIY stainless electropolishing

[J.B. Welding]

Not sure if it's in the right section but.. I've had things electropolished in the past and it's the b'all and end all of processes for getting a good mirror/marine resistant finish on 316 stainless. It is, however, a 'send it off and play the waiting game' process and that drives me as I like to control my destiny work-wise.
Soo.. does anyone know the current/electrolyte/time factors involved in a home made set-up? Anyone had any DIY success with electropolishing? All help gratefully recieved! P.s. I do like a big Current

 

[hotrodder]

I cobbled together a home made electrolytic weld cleaning machine a few years back which works on basically the same principle. While it'll kinda electropolish small parts hung in a bath the results are nowhere near as good as stuff subbed out to the pros

There are various electrolytes that can be used but AFAIK all of the flavours used by the pros are pretty nasty compared to what's used for weld cleaning... phosphoric acid is typically common to both but 'proper' electropolishing recipes often (usually?) contain significant amounts of sulphuric or chromic acid too. Straight citric acid works (albeit a bit slowly) for removing heat tint and slightly improves overall surface finish (more through passivation than electropolishing) too but leaving the parts in for longer doesn't help and often dulls them a bit

Can't remember the ratios off the top of my head but i did make a note of a recipe using phosphoric acid, propylene glycol, isopropyl, water and a dash of soap that's supposed to work. Searching the internet for 'DIY electropolishing' will probably find it, i kinda lost interest beyond weld cleaning as to electropolish anything bigger than very small parts really needs a properly butch power supply and while it may not be an issue with a properly big tank a small bowl of electrolyte gets 'kin hot with just a 400ish W 24V DC power supply that i use for small bits/weld cleaning. Then you need room for a decent size tank, suitable ventilation (fumes + hydrogen production), more toxic waste to deal with etc.
12 - 18V and something like upto 40A/dm^2 are the more usual numbers for electropolishing AIUI so a car battery should do the job for experimenting?

 

[henry Kadzielski]

Good morning gents
I have a locally produced weld cleaning and polishing system produced here in Au. Whilst the weld cleaning and passivation I use quite frequently, the polishing not so. The chemicals used are now not so aggrecive and the system relies on the heat produced by the DC current to activate the chemicals. This works OK, there are several machines of different capacities to suite you individual applications, however 'cost a lot'. The electro polishing however effective is slow by comparison. On larger surfaces it is faster to mechanically abrade the surface and get it to almost the right finish, then use the electro polish to finish off. Otherwise the process takes too long and generates much heat and fume. I have done this and also have been demonstrated by the manufacturer, the pros and cons of both ways.
Yes it will do it from a raw state, but boy it tales a long time and the heat you can cook on the finished material

 

[henry Kadzielski]

Oh I forget to mention, the machines also do marking. On dull finish or mill finish you use a manufactured stencil and the marking fluid, apply the correct steeing on the machine and it will produce a blackish etched result. This will not wash away and is etched into the material for life. On polished material the same stencil with differant fluid and a setting change it will etch the bright polish and leave a mark there for life. I have seen this just two days ago and have ordered the marking kit for myself. It is not for everyone, however I like to show where the 'bits' came from

 

[J.B. Welding]

Thanks for that. I can see the aquisition and disposal/stroage of said liquids could be a burden. I would probably need a couple of hundred litres to do big enough batches with the time involved. The weld cleaning is secondry to the large ammount of tube and plate to get shiney. Seems like it could be an expensive task to get a finish like they do at the plant. S'pose there is always Autosol
Henry I've recently seen reusable transfers that are applied with a tig-brush and are permenant-is that the same as the things you are talking about?

 

[henry Kadzielski]

Good morning JB Welding
Yes it is tig brush that I have. And yes they cut the one off stencil for you from a pdf file. I have to 700 purple one had to wait 6 months for it, till they had their first production run, no substitute for hore spower, have now had it for many years. And yes there are several manufactures of these machines in AU. I have mostly delt with Chris, whom it the only one you can get any sence out of. He also does travel to europe, asia and the US to promote the machines. I suspect the others do likewiswe.

 

[Jrstainless]

I have one of these I'm looking to offload cheap.