Electrolysis for rust removal?

[kalel]

I'm not sure if Repair is the best section, but only in repair is the discussed technique useful. I would never subject a new product under warranty to rust removal techniques.

I've seen some videos regarding rust removal using electrolysis:




None of the above are really aimed at electronics, but that shouldn't mean the same technique can't be used in some cases where there's a rusted metal part which can be removed for cleaning. Are there such cases in electronics? I'm thinking of perhaps battery contacts/springs, but I have no idea if it would be suitable for that.

If there are potential useful cases, I would have some questions about the procedure:

- They mention using cleaning/washing soda to add conductivity. Can other things, e.g. salt be used, or would they cause some negative effect?
- Do the electrodes need to be metallic for this to work, or could you use e.g. graphite rods?

[helius]

The only variation on this technique that I know suited to electronics repair, is brush electropolishing. The absorbent brush is sleeved around a metal electrode, and the other terminal of the power supply is connected to the circuit board through copper tape.

I would think long and hard before using any electrolyte containing chloride, as this type of ionic contaminant can cause copper corrosion over the long term. The use of sodium carbonate is pretty safe, as are sulfuric, phosphoric, or oxalic acids. The use of acidic or basic electrolytes depends on the types of metals to be treated and I'm sure you can find information about this.

[jpanhalt]

I have used that method myself several times.   There used to be a "dip strip" place in town that stripped whole cars (it also can remove paint).   For stripping rust and paint, a hot solution of trisodium phosphate is used (I suspect there were other things in the tank.)  EPA requirements shut down the commercial outfit.  I suspect paint might also come off in the home process too.

One advantage of phosphate is that the steel/iron comes out "phosphated."  That is a recognized type of metal prep for ferrous alloys.

The pieces I did at home were only steel.   The hot dip process mentioned destroys active metals like aluminum and pot metal.

John

[Rerouter]

Using a table salt electrolyte I was able to accomplish the same, but far slower and at very low currents, I used a hardened steel nail as a sacrificial electrode
Your mileage may vary.

I used a very weakly biased AC waveform, the bias was about 1.6V on a 7V AC pk-pk waveform, it ends up polishing the surface if you get the bias correct, it rips off a bit of rust, and then plates a bit of the nails metal, going round and round in circles slowly removing material, but preventing pitting.

if you keep the spacing wide enough, the oxide just falls to the bottom of the tank, leaving the metal from the nail fairly clean,

I ended up leaving it over 4 hours, with about 5cm seperation with a heavily rusted screwdriver slowly turning it every half hour, all the rust came off after about 3 hours, and the metal began shifting from black oxide to yellow tinged silver towards the 4th hour, after removing it from the bath the yellow wiped off revealing the shiny base metal.