Rust Never Sleeps… Part 3

I’ve previously written about rust prevention, and light rust removal, which accounts for somewhere in the region of 95% of my rust management needs, especially as I don’t tend to buy many old tools. But occasionally I do have the need to refurbish antique tools, and when I do the light rust removal strategies I’ve written about previously don’t really cut it. So something a little more aggressive is needed.

Amongst the tools I inherited from my Grandfather was his set of pre-WWII carving tools. By rights I shouldn’t have these tools – my Grandfather was supposed to hand them in to be melted down for Spitfires during the Second World War, but instead hid them under his bed. Which although a poor contribution to the war effort, does at least mean that I have some of the tools my Grandfather owned as a boy.

Fast forward some 70 years, and the carving tools were suffering from an unhealthy accumulation of rust from years stored in a damp workshop. Although my Grandfather had been rigorous for as long as I can remember about sharpening and oiling his tools in preparation for winter, his final years saw his workshop start to decline, due to ill health and advanced years. So four years ago when I inheritated his tools, I knew that some time spent on tool-rehabilitation would be necessary. I’ve been slowly refurbishing the carving tools in pairs (because doing the full set of 14 in one go sounds a lot like work, and I’d rather be building things than fixing up too many tools), and this seems like the perfect time to finish my occasional series on rust management strategies.

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Two gouges in a solution of citric acid and hot water.

Fortunately with some basic chemistry, and a bit of elbow grease, most tools can be cleaned up relatively easy. My preferred method to remove severe rust pitting is citric acid, which can be purchased in powder form for a low cost from Amazon, or home brewing supplies. The powder is mixed with water (I use hot water as the higher temperature acts as a catalyst) to the desired strength, and tools submerged in the mixture overnight. For carving tools and small plane blades I use an old jam jar which also allows me to keep wooden handles out of the water. The citric acid attacks the rust while leaving healthy metal unscathed, and unlike the more specialized rust removal solutions, can be poured down the sink without any risk of environmental damage. You don’t even need to wear protective gloves when using citric acid, unlike the more aggresive forms of anti-rust chemical warfare. All of which makes using it a stress (and risk) free experience.

 

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These gouges have just come out of the acid solution and are ready to be cleaned up with a brass brush. It is easy to see here which section of blade has been treated with the citric acid.

Once the tools have had the worst of the rust removed in the citric acid bath, I dry them and remove the remaining rust with a stiff brass bristled brush. A steel brush may be more aggressive, but also runs the risk of magnetising the tool blade, which I’d rather avoid. Going slowly with the brass brush works just fine, and to be honest if I’ve mixed the citric acid to the correct strength it doesn’t take much to remove the last of the rust. What is left is a dull, but clean blade, ready for sharpening.

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After being cleaned up with the brass brush, these gouges are ready to be sharpened. You can see clearly how the previously rusted length of blade is much cleaner than in the previous photo.

To sharpen the carving tools I used a combination of scary sharp papers on some 10mm thick float glass for the outside edge, and some Arkansas oil stone slip-stones for the inside bevels. The whole process only takes a couple of hours of workshop time, plus a night or two of letting the tools soak in the citric acid solution, and these carving tools are now good to go for another 70 years or so.

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Translucent Arkansas slip-stones are ideal for sharpening carving tools.

6 thoughts on “Rust Never Sleeps… Part 3

    • James, there’s not much science to it – I tend to fill a jam jar with enough hot water to cover the rusted metal, and then add 2-3 tea spoons of citric acid. Give it a stir and come back 30 minutes later to see if anything is happening. If not then I add more powders I probably should be more scientific about it, but so far it’s worked well for me.

      The only downside to citric acid is the strong smell of sulphur as the rust dissolves, which may or may not be to your taste 😉

    • My citric acid measuring is about as scientific as Kieran’s, but it has also worked well for me. If it’s strong enough, it will sting all the nicks and cuts on your fingers and cause bubbles to form on the rust after a short time.

      The biggest benefit for me (over vinegar): I can store about 10yrs worth of citric acid powder in the space of one vinegar bottle.

      • Thanks Colin, that’s the best tip I’ve seen on this subject. I’ll give it a try! I already have some citric acid powder from my home-brewing days. 🙂

  1. Hi Kieran, it’s lovely to see someone else refurbishing old tools. Nearly all my tools came to me covered in rust and totally unusable. I’m currently restoring a non-matching pair of side snipe planes, to add to the moulding plane section of my ATC.
    I have never bothered treating the rust, other than rubbing it down with wire wool and oil. Since you must polish the ‘back’ of the cutting edge (inside of your gouge) to a smooth shiny surface before you can get a truly sharp edge, that’s the only bit I concentrate on, using diamond stones or wet & dry around a dowel, and then honing compound. I have glued some suede to dowels for this.

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