Why does it need to be biodegradable. You want something that will give long lasting protection to the tool and not decompose; not something that is going to protect the environment. from the milliliter of solution you put on the tool.

For some of your tools you may consider car wax. I clean my table saw and use a good grade of car wax on it, I do the same for hand saws and the metal unpainted parts of other tools.

For some just cleaning and storing in a dry contain may be sufficient. For other a light coat of any oil, (motor oil, 3 in 1, or others ) will protect the surface. Motor oil by design is made to stick on the surface and has chemical to protect the surface it is on.

Whether you use wax, oil, or what ever you need to pull the tool, and clean if necessary. You should reapply the surface protection you choice periodically. Some this may be need after each use, or several. For my table saw, i do it 3 or 4 times per year, when ever I am in the garage, and have a few minutes. If I use it heavily for a couple days I may also clean and rewax.

@krnuttle Biodegradable is more about not needing to worry that it is on my hands or how to clean it off. I apply every time I use the tool, so every few days....

Maybe the problem with mineral oil is that it comes off too fast.

Use paper towels to apply and then wash you hands with soap. If you are really afraid of the oils use rubberized gloves.

Felco 990 is a grease, not an oil. And you are already using mineral oil- a non-biodegradable oil. Neither will hurt you if you get a little on your hands, just wash your hands or wear gloves.

If you are really worried about it being biodegradable and even more safe for touching, you can try using boiled linseed oil or food-grade camellia oil. They won't last long and will still require regular applications.

If you are having rust development issues- clean, dry, and oil your blades more effectively and more often. Perhaps consider getting your blades sharpened or replacing them with fresh blades.

Japanese tool makers often suggest camellia oil but often what you can buy is actually a mixture of mineral oil and camellia oil. If I remember correctly, pure camellia oil does not last long and that mineral oil helps it last longer.

The OP was worried about oil to skin contact and biodegradable factor, so thus the suggestion for food-grade camellia oil and the warning that it does not last long. Food-grade should be just camellia, no mineral oil.

I should have been clearer. What I wanted to say that camellia oil does not last much in storage. At least that is what I recollect.

I often use camellia oil + a few drops of clove oil because I like the smell. It's said that camellia oil is what the Samurai used to protect their sword blades.

Observation only: the best product I've used as a rust preventative is American Bonsai's XOil.

Al

FWIW - AB was at the last show I attended and had a pair of iron concave cutters soaking in half a jar full of water, protected with the XOil. There was some discoloration, but no rust ...... and they said the tool had been in the jar for more than a month. You've seen my work station .....

(Chinese quince ^^^ )

Almost all the black steel tools are Masakuni, and I store and use them in my unheated garage over winter. As you can imagine, the RH gets up around 100% when snow is melting off the cars, so the tools need protection. Both the camellia oil and the XOil need reapplying after each use if the tool is to be fully protected. Sort of like a gun - they should be cleaned and wiped after each use with something to remove salts from our hands, and coated with a light film of a good protectant to thwart rust/corrosion. I'm not as careful during the summer months, unfortunately, so some of the tools w/o cutting edges don't get the same care as the cutting tools and have some small pits as witness to my sloth. Live and learn, over and over ..... better to be wise than learned.

Al

I may have forgot my chemistry, but submersing a tool in water to demonstrate a product's protection qualities is a bit deceptive. Rust is the oxidation of he metal. The most corrosive environment is a damp tool in air where there is a lot of oxygen to attack the tool. In water, he only oxygen comes from that dissolved in the water its self.

I checked the price of the American Bonsai's XOil. At $20 dollars for 2oz of the product, $160/gal. it better not only keep the rust away but keep it polished while in storage.

There are much cheaper products that will do an equally good job,

The tool was soaking half submerged in a glass quart jar, so from the waterline upward, the tool was subjected to close to 100% RH; as you noted, a very corrosive environment which makes the demonstration an effective display of the product's ability to prevent rust/corrosion. Why jump to the conclusion the tool was submerged, just so you could put forth a pooh pooh theory re the product. I grant the product is expensive, but that's for the individual to weigh.

"There are much cheaper products that will do an equally good job," So ..... what are they?

Al

@tropicofcancer (6b SW-PA) I ordered the camellia oil and I love it. It has perfect viscosity for this task, both for lubricating the joints as well as for spreading over the tool surface.

I ordered the Felco oil and that was a disappointment. It is like a heavy industrial oil that you might use on a cylinder bearing thousands of pounds of weight. It does not form a liquid easily and it is hard to get off the hands.

I am willing to try the XOil someday if they ever get onto Amazon.

Glad you liked it. I keep a micro-fiber rag lightly soaked in oil in a ziplock bag. I used that to quickly wipe my tools. Or you can also make a rag in a can oiler: https://www.youtube.com/watch?v=npKo1y2e8RI Convenient for woodworking tools that are flat. I find just the plain rag more useful for bonsai and gardening tools.

You will also like Sandflex blocks: https://www.amazon.com/Sandflex-Sanding-Block-3-Pack/dp/B000GACU1Q/

I use them to clean gummed up tools and for polishing the metal. They are like sandpaper and eraser combined. The abrasive is embedded in a rubber like material. Does not the damage the tool. I mostly use the medium for removing dried up sap and slight rusts and the fine one for polishing.