De-rusting

[Alistair D]

I was watching an episode of the repair shop on BBC1 last night. The item in for repair was an old and quite rusty treadle Singer sewing machine. Part of the restoration plan was to remove the rust but still leave it showing it's age. The method they used was electrolysis. That was a new one on me so time for a bit more investigation.

There are a number of websites that cover this method and the link I have chosen is only one example.

https://www.instructables.com/Electrolyt...aka-Magic/

It struck me that this might be a good method for de-rusting radio chassis etc.

Al

[Nick]

It's a very common technique with tool & car restorers - there's a lot out there about it. Dri Pak, who make the familiar green Soda Crystals packs you get in the UK, have a small page about it: https://www.dri-pak.co.uk/helping-restor...omponents/

I mostly use phosphoric acid which is really cheap to buy in bulk - a lot of the commercial rust-converter products are actually phosphoric acid in a carrier medium (maybe a gel to help it stick to vertical surfaces etc.)

I use both techniques prior to using a Zn plating line - current car restoration is an old Landrover 90 - well known for its rust issues...

Phosphoric acid is good stuff!

[Cleggy]

The problem with electrolysis is that current likes to take the shortest path so it may be tricky getting the inside of the chassis to clean up, especially the internal corners and metal behind a fold.

With phosphoric acid, isn't it the case that you leave a layer of metal phosphate on the surface and I'm not sure that all paints like going on to a phosphate layer. However, it is useful where heavy pitting is difficult to remove by mechanical means. The old traditional Jenolite (remover) works, but their newer product (converter) is pants.

For a radio chassis, citric acid solution is a very good alternative; buy it as a powder from Wilko or ebay. You can find lots of info about using it on the web. It won't leave a surface film and the metal should be painted ASAP before the risk of flash-rusting occurs.

[BusyBee]

The problem with electrolysis is that current likes to take the shortest path so it may be tricky getting the inside of the chassis to clean up, especially the internal corners and metal behind a fold.

I think that this is probably a bit of an issue with any method as a layer of grease on an internal corner will be difficult to clean out. That's maybe why some of the chemical methods work better as they would de-grease it better. In principle the electricity takes all routes but with limited current flow through the more insulated areas. Perhaps a point to be thought about when the chassis has riveted fixings. Don't electro-plating companies thoroughly de-grease items to be plated first?

As you say, areas behind a fold will get poor application. I suspect with most / all methods.

Tracy

[Nick]

The problem with electrolysis is that current likes to take the shortest path so it may be tricky getting the inside of the chassis to clean up, especially the internal corners and metal behind a fold.

I think that this is probably a bit of an issue with any method as a layer of grease on an internal corner will be difficult to clean out. That's maybe why some of the chemical methods work better as they would de-grease it better. In principle the electricity takes all routes but with limited current flow through the more insulated areas. Perhaps a point to be thought about when the chassis has riveted fixings. Don't electro-plating companies thoroughly de-grease items to be plated first?

As you say, areas behind a fold will get poor application. I suspect with most / all methods and you need the right electrodes in the right places.

You have to have multiple electrodes apart from the workpiece (anodes or cathodes depending n whether you're doing anodic or cathodic cleaning).

It the same with plating - the workpiece has to be as clean and degreased as possible before you start.

See https://www.corrosionpedia.com/definitio...c-cleaning

[Cleggy]

I've tried electrolysis for de-rusting....just once, and then moved on. If I could find plenty of graphite rods that were suitable, I might take another look. The combination of the high-speed wire brush and citric acid, Rule!

[Bushbaby]

I have an old cast iron stand for my Myford ML 3 lathe but its absolutely rusty (its an old barn find). I have never got around to cleaning it (it might be a bit to heavy for me lift too now as well). Could it surface cleaned by electrolysis (I think it might be a wee but hard to do so?).

   

[BusyBee]

I have an old cast iron stand for my Myford ML 3 lathe but its absolutely rusty (its an old barn find). I have never got around to cleaning it (it might be a bit to heavy for me lift too now as well). Could it surface cleaned by electrolysis (I think it might be a wee but hard to do so?).

Wouldn't that be a better candidate for sandblasting?

[Bushbaby]

Cost of sandblasting is expensive.

[Nick]

Cost of sandblasting is expensive.

Depends what you call "expensive". I am restoring an old Land Rover at the moment, so having quite a few things shot-blasted and stove-enamelled.

Looking at that stand, I would have thought around 30 quid for shot-blasting, possibly slightly more. Certainly more if the shop put a primer on the clean metal to stop instant corrosion.

Depends where you live, if cash changes hands, who you know etc.