The citric acid experiment

[Moses Yoder]

A while back I bought some rusty files and somebody was talking about citric acid. They said they dumped in 2 or 3 small tubs in a bucket and left the files in for a week. I thought I would try it. My mom gave me a square plastic container that used to hold mush when she worked at the restaurant, holds about a gallon of water. I bought a small container of citric acid, I am not sure what size, maybe 4 ounces. I dumped it all into the water and stirred it then entered the files, covered it with aluminum foil.

After a week I took the foil off and found the files congealed together into one lump sum. I pried one off. It had a gooey black coating on that was impossible to clean. I decided to chalk that up to experience and covered them back up to eventually throw in the trash. Sunday I saw them again and pulled the cover off and one of the files popped loose right in my hand. It cleaned up nice and I was hopeful for the rest of them. Tonight I set up to clean them and found the first one too gunked up with a layer of white stuff to be cleaned. Way too much effort to clean. I rescued the screwdriver blank I had thrown in with the files and threw the rest in the trash.

I think maybe there was too much citric acid in the water.

[Zach Dillinger]

I've sharpened vixen files and rasps in vinegar, but I've never left them in the "soup" for more than about 24 hours. A week seems way too long.

[Joe Tilson]

Moses, I have found a quarter of a cup to on gallon of water does very well. I would never leave a file in the soup for more than eight hours, and it would have to be in very bad shape. Found a few Simond and Nicholson USA file here and there which turned out very well. I use a brass brush across the teeth to get the black stuff off. They all cut very good. I have also used vinegar to clean them up, but it's a little slower than citric acid. Hoping the best for you on cleaning up what you have.

Joe

[Bernadette Semilla]

I prefer citric acid for derusting as I don't have to feel bad dumping it in the sewer grate (I remember painting yellow fishes above them as a kid...) and don't think I've ever let my rust baths go a whole week. I usually check on it often to turn tools around and brush off the loosened rust. I have noticed citric acid gets sticky and can have a haze? miasma? of stickiness at the bottom, especially after left to it's own devices. This is probably the culprit! Live and learn, right? :)

[David M Anderson]

I use plain ol lemon juice on most of my rust removing on hand planes.
Usually just leave in for 8-10 hours. If I am going to repaint I use brake cleaner to clean the lemon juice off.

Before cleaning with lemon juice.
294354

Metal parts after...

294356

Lemon juice..

294357

I have tried vinegar and etching of the metal occurred.
Electrolysis works the best though.

[Malcolm Schweizer]

I thought you liked rust!

[Derek Cohen]

A while back I bought some rusty files and somebody was talking about citric acid. They said they dumped in 2 or 3 small tubs in a bucket and left the files in for a week. I thought I would try it. My mom gave me a square plastic container that used to hold mush when she worked at the restaurant, holds about a gallon of water. I bought a small container of citric acid, I am not sure what size, maybe 4 ounces. I dumped it all into the water and stirred it then entered the files, covered it with aluminum foil.

After a week I took the foil off and found the files congealed together into one lump sum. I pried one off. It had a gooey black coating on that was impossible to clean. I decided to chalk that up to experience and covered them back up to eventually throw in the trash. Sunday I saw them again and pulled the cover off and one of the files popped loose right in my hand. It cleaned up nice and I was hopeful for the rest of them. Tonight I set up to clean them and found the first one too gunked up with a layer of white stuff to be cleaned. Way too much effort to clean. I rescued the screwdriver blank I had thrown in with the files and threw the rest in the trash.

Hi Moses

That "someone" was me.


I think maybe there was too much citric acid in the water.

Indeed! It is very likely that the citric acid powder you used was stronger than mine (I bought it at the local supermarket bakery section). Either that or the steel we have Downunder is more durable (like our wood) :)

In any event, although I left the files in a bucket for a week, I checked them every day. There was minimal gunking up, even after a week.

This process has a tendency to create flash rusting if you wash-and-dry. Immediately oil (easier to spray as the teeth are sharp) and brush the oil in.

My experience has always been excellent. I have done this a few times now, and always had good results.

You may wish to question why your mum's cakes have a little extra "bite" and zestiness next time you bite into one! :)

Regards from Perth

Derek

[Peter Evans]

In any event, although I left the files in a bucket for a week, I checked them every day. There was minimal gunking up, even after a week.

This process has a tendency to create flash rusting if you wash-and-dry. Immediately oil (easier to spray as the teeth are sharp) and brush the oil in.

My experience has always been excellent. I have done this a few times now, and always had good results.

I have seen the gunking effect whilst experimenting with citric, and it is very difficult to remove. Derek's advice is correct - check the files/rasps regularly (every fwe hours) and remove when sharp (enough), rarely is this more than 2 days with a fairly weak solution (I often use a solution that has already been used to derust tools to sharpen files).

I do not oil after acid sharpening. Immediately after rinsing, brushing off any gunk that has formed, and washing clean I hit the file with a hairdryer and ensure it is hot and bone dry. Then I wrap in newspaper and store in a box - I do not find sharpened files rusting after this treatment, and Sydney is somewhat wetter than Perth...

Cheers
Peter