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| PK:
This is another 'we're doing this at work, but everything is relevant to y'all at home' projects. We've been buffing some TIG welded stainless assemblies for a few years now and it's a bit of a pain: 1.You get a shiny weld which contrasts the satin finish on the rest of it. 2.You have to get the wax off. 3.Then you have to get the stuff you used to get the wax off, off. We could just use pickling paste, but all the ones that work have HF acid in them and that's nasty even by my lax workplace safety standards. I decided to look into electro-polishing and a quick search turned up a candidate solution of Citric and Sulfuric acids, neither at nasty concentrations... This looked promising as I'd assumed we would have to use hot phosphoric/sulfuric acid. Out came an old mop bucket, in went some lead flashing for a cathode, and 7 minutes at 10A later out came the part. All it needed was a quick wipe under running water and presto! I've started a thread on this, because I think I'm going to automate the process and that should be interesting... PK |
| Will_D:
If you can't get the part into the bath then you need to buy (or make) a carbon fibre brush and use that as the anode and paint the oxide film away. I used 50% cold phosphoic acid iirc. For the brush i just pulled carbon fibre cloth into a 6mm copper tube, flattened end to trap fibre, attach wire an the wrap the copper in inulating tape. I used a 8 amp 12 volt power supply. Idea ripped off a commercial set up!! like this: http://www.weldcleaningsolutions.com/weld-postcleen-kits.html |
| simon.baldwin69:
Hydrochloric and nitric acid makes a great pickling paste Sent from my EVA-L09 using Tapatalk |
| Will_D:
Nitric acid is getting very gard to obtain these days |
| PK:
--- Quote from: Will_D on August 28, 2017, 09:57:35 AM ---If you can't get the part into the bath then you need to buy (or make) a carbon fibre brush and use that as the anode and paint the oxide film away. I used 50% cold phosphoic acid iirc. For the brush i just pulled carbon fibre cloth into a 6mm copper tube, flattened end to trap fibre, attach wire an the wrap the copper in inulating tape. I used a 8 amp 12 volt power supply. Idea ripped off a commercial set up!! --- End quote --- I did some experiments about a year back with a system like this. I used some carbon from some reinforcing cloth. It works well for a hobby environment, but each case has just under 1m of weld so you'd be standing there for a while I used rust converter (ie phosphoric acid) which I'm not as happy about as citric acid. With a tank, you just throw it in and go do something else for 5min.. |
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