Thread: Oh dear, my tools have suffered - rust!

Chelating acid rust removal eg Acetic, Citric, Oxalic will get rid of it. When done don't wash the acid off but blow the acid off the blade with compressed air. Molasses is another but it is very slow. Oxalic leaves a yellow residue so unless you don't care about this or are going to paint over delisted object then use one of the others.

The other method is electrolysis. But once you have done Chelating acid rust removal, unless you need to remove paint as we'll as rust, electrolysis is more of a hassle.

My go-to has been simply white vinegar. After soaking for a couple of days the rust simply wipes off, unless really bad, in which case subsequent baths may be required.


Bob, is your comment about not washing but rather blow the acid off in order to prevent the "flash rusting" if not coated with oil almost immediately? I learned the hard way that when cleaning tools with vinegar that there will be no patina to speak of to keep the rust at bay, and will develop a light rust within minutes after washing unless oiled. If there's an easier way, I'm all ears.

If the rust is only light,
I would at first, just try some scotch bright pads.
Any good paint shop or hardware store will carry them.
Start with grey which is the finest.
Followed by some light oil or wax.

Cheers Matt

Evaporust is awesome for this, plus has the added benefit of not damaging the handles (allegedly) or the metal.

Supercheap autos used to stock this.

Regards,

Adam

After Bob's contribution, and speaking to a friend who is heavily into restauration of old motors (dairy shed type motors, and a collector of old tools)
I went out and spent some money on a phosphoric acid solution. Currently have the first 6 or 8 chisels sitting in that, timer set for 35 minutes.

The one chisel I tried with baking soda electrolysis has cleaned up, but to do that with all my chisels sequentially would be
a bit of a pain, particularly if checking on progress from time to time and running each for 2 hours or longer.
I have one more in that bath right now, that is an odd size.

We'll see how all that pans out.

Originally Posted by P.W.H.

The one chisel I tried with baking soda electrolysis has cleaned up, but to do that with all my chisels sequentially would be a bit of a pain, particularly if checking on progress from time to time and running each for 2 hours or longer.
I have one more in that bath right now, that is an odd size.

We'll see how all that pans out.

You can easily electrolyse the rust simultaneously from a bunch of gear. - suspend the positive electrode from the middle of the container and arrange all the chisels around the inside of the outside of the container all connected to the negative - ensuring none are touching the positive electrode.

I have also simultaneously use several containers made out of 100 and 150 mm PVC pipe/ducting, daisy chaining all the "+" and "-" together.
The PVC pipe is sealed at the bottom with cemented on end cap. Onto top I add a threaded coupler so that it has a screw top lid for safe storage.

Provided you connect the + and - correctly you cannot damage any metal.

The best material to use as the positive electrode is a carbon rod. Using any sort of regular steel ends up making the electrolyte a sludgy orange and covers the electrode with an orange layer that is nonconductive so it slows down the process and has to be scraped off to get the reaction going again.

Instead of baking soda (sodium bicarbonate) I use foot bath salts (sodium carbonate).

I did use the phosphoric acid, 2 batches of tools in a 5l bucket, 35 minutes each, excellent results.
Also two gouges in the electrolytic setup, worked just as well, and oh, aren't you right about the orange sludge!
I used a piece of chrome plated steel pipe from a dead lamp as anode.

Anyway, all my chisels/gouges/parting tools look good, there's some grey surface rather than shiny steel, but no visible rust.
I've recovered the acid, I'm sure it will be good for several more applications.

Brown vinegar, cheap as chips and works easily.

Only one comment to add.

If the flutes on the gouges are only very slightly pitted after all of the de-rusting is completed you may not get a good edge when you sharpen the bevels.

The cutting edge is formed by the intersection of the flute and the bevel surfaces.

If any pitting on the flute is deeper than the grind marks that you will leave on your bevel from grinding then that will give you a sub-optimal edge.

In that case, the flute will benefit from a grind/polish at least for and inch or so from the tip.

Originally Posted by NeilS

Only one comment to add.

If the flutes on the gouges are only very slightly pitted after all of the de-rusting is completed you may not get a good edge when you sharpen the bevels.

The cutting edge is formed by the intersection of the flute and the bevel surfaces.

If any pitting on the flute is deeper than the grind marks that you will leave on your bevel from grinding then that will give you a sub-optimal edge.

In that case, the flute will benefit from a grind/polish at least for and inch or so from the tip.

I have found a rolled up 320 0r 400 grit sandpaper makes a nice hone for the inside of the flutes.

Oxalic acid (Diggers Rust & Stain Remover) about 100g diluted with 10l water is excellent and not too aggressive (like vinegar) and cheap-as compared with Evaporust etc.

Let the metal sit in the solution for 1-8 hours depending on the amount of rust. Brush all parts every hour or so to remove the loosened rust. Plastic bristled brush only. I wouldn't leave anytjing it overnight unless it is seriously rusty and not an edge tool.

Remove and wash off residue once the metal no longer bleeds off any orangey rust colour when lightly brushed.

If you follow this routine no yellowing should occur. Yellow staining means the metal has sat in the solution too long, but can be polished off.

It is also excellent on lightly rusted chromed parts.

This oxalic solution can be kept for future use for months and months unlike vinegars, citric, etc.

V

Fortunately the rust was only light surface rust in this case, so ... ah, I forget, is it iron phosphate you get or some more complex molecule, but whatever, the light surface rust got converted into a fine grey coating that will keep more rust off for a good long while. No pitting, so I have no problems sharpening. The 2nd hand Tormek I bought does a great job. Just need to re-vitalize the leather polishing wheels. That's next on the list.

Originally Posted by dubrosa22

Oxalic acid (Diggers Rust & Stain Remover) about 100g diluted with 10l water is excellent and not too aggressive (like vinegar) and cheap-as compared with Evaporust etc.

100g/10L of Oxalic (0.1%) is quite dilute, whereas normal vinegar is about 4%.

I've done extensive testing of mild steel in various acids and found that at the same concentration Oxalic dissolved about 4x more than then Acetic .
see Solubility of mild steel in various rust removal acids.)

After 115 hours (~5 days) of soaking in 4% Acetic, Citric, Oxalic and HCl the weight losses were
Acetic 0.48%
Oxalic 0.12%
Citric 0.25%
HCl 4.0%

Hi all, went the vinegar route with a couple of forstner bits the had firly heavy surface rust left them in overnight. Next morning the rust was all gone but left me with two jet black forstner bits. Anyone know why that would happen. Brian.