Removing rust – the experiments (iv): liquid rust removers

To test the liquid solutions, I used a series of  vintage blades with varying levels of rust – it is challenging to find four blades rusted in exactly the same way. Each blade will be submerged halfway in a rust removing liquid – vinegar, molasses, citric acid, and oxalic acid. The blades were chosen for their ingrained rust – rut that had been on the blades for years, perhaps  more than a decade (or two, or three?).

Experiment 1: Vinegar

Liquid: 250ml of white vinegar

The first experiment involved placing a blade in vinegar. I used white vinegar – although I would imagine cider vinegar would work just as well. After about an hour you can physically see the vinegar working, with small bubbles forming in the solution. The vinegar stripped the rust from the blade within 8 hours. The rust was almost lifted off the surface of the steel, forming sheets of precipitate, which slid off the blade into the base of the jar.

Vinegar seems to be extremely effective in removing rust, and leaving a very clean surface. It is also probably the cheapest form of rust removal there is, however one has to be somewhat cautious, as it is an acid, and parts left too long in the solution might experience some etching. If you look closely at this blade, there is substantial pitting, but in this case that is the long term action of the corrosion itself.

A little too much pitting perhaps?

Experiment 2:  CITRIC ACID

Liquid: 25g of powdered citric acid to 250ml of water

The citric acid also stripped the rust from the blade in under 8 hours. Unlike the rust flakes produced by the vinegar, here the rust came off the blade in small particles, and settled to the bottom of the jar.

A cautionary note here, that citric acid is corrosive, so care has to be taken when using it. This blade also had pitting, again the result of long term corrosion.

Experiment 3:  Evapo-rust

To be honest I was not going to bother with using Evapo-rust, largely because of the previous post on the Stanley No.15 rust-heap – we know it works very efficiently. However, from the perspective of speed on these plane blades, it seems like the Evapo-rust is one of the slower performers. After 48 hours there was little to no activity on the blade, and I tried a second blade in another jar – it too showed little activity in the 24 hours it was soaking. To test that I am not loosing my mind, I placed a rusty lateral adjustment lever in EvapoRust from the same container – and it actually worked (see next post). I then checked the blade from the Stanley No.16, and noticed it too had mediocre rust removal. The image below, like those previous is the original blade on the left and the post-rust removal blade right. It’s hard to effectively tell them apart. It has removed some basic surface rust.

My conclusion from this is that possibly EvapoRust does not work that convincingly on hardened steel, but works great on iron, or cast iron plane parts, e.g. bodies, lever caps, etc. Hardened steel might not be the right consistency to produce the chelating effect that Evapo-Rust relies on (ideas/comments? – I could find any info anywhere, and am yet to receive an email back from Evapo-rust Canada).

Experiment 4:  Molasses

Liquid: 50ml molasses to 250ml of water

With a ratio of 1:5  this was the slowest performing of all the liquids. I had this blade soaking for 48 hours in the molasses, after which I gave it a scrub with a scouring pad. The results are quite good, with the rust being removed from the blade. I imagine leaving it for 72 hours would be ideal.

I would say that if you had some rust that needed a long soak, that molasses may be the way to go, even with boosting the ratio to 1:4.

FINAL remarks

Below is a close-up of all four blades. I would have to conclude that the vinegar produces the best result on plane blades, and I would imagine the cheapest means of removing rust. Citric acid is a close second.

And for those interested, here is what the residue looks like for the vinegar (left) and citric acid experiments:

Vinegar vs. citric acid rust residue

 

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7 thoughts on “Removing rust – the experiments (iv): liquid rust removers

  1. ericfromdayton says:

    I recently got some Goof-Off Rust Aid (outdoor) at Lowes for $10 a gallon. It was used at work on the metal siding and cement pad to remove some rust stains. It worked really well. Later tried it on a thick metal work table that had been outdoors for a year. It definitely was dissolving the rust and like you found with some of the others, a little scrubbing speeded the process. I think it actually worked a little better than the Evapo-Rust. Goof-Off Rust Aids active ingredients are Hydrofluoric Acid and Oxalic Acid. Warnings include not touching it, well ventilated area etc.
    It needs to be rinsed off when done or the dissolved rust will rebuild itself. Have not tried it yet on hardened metal. Based on your tests I will probably try vinegar to clean some of my tools. Thanks for the great research.

    • Matt McGrane says:

      To EricFromDayton, be very careful with that hydrofluoric acid (HF). Though I’m sure it is in very small amounts in the Goof-Off product. We used to use HF where I worked and I was told that when HF contacts the skin, it will search out calcium (bone) – it’ll eat right through skin and other tissues to get to the calcium, leaving behind some serious skin necrosis. Ugly stuff!

  2. spqr says:

    Thought I would add this as a comment. So, I emailed Evapo-rust re: the rusty blades that were the same
    after 48 hours in ER. Here is their response.

    Me:
    Does the type of steel make a difference in how effective Evaporust will be?
    reply: Where did you purchase the product?
    Me: Lee Valley. It works perfectly on cast iron, and I have de-rusted a number of block
    planes… however I have tried three old block plane blades, all hardened steel, and
    after 24-48 hours there is no derusting. I then tested the solution
    on a rusted lever cap, which worked fine.
    reply: Sounds like a problem with product?
    Me: No, it works on products which are cast iron… but not items made of hard steel.
    reply: Purchase another bottle from another supplier.

    No real conversation, just one-liners. Interesting customer service…

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