Applying a light patina to carbon steel?

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biogon

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Jan 2, 2002
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Yesterday I received a carbon steel japanese-style fixed blade -- one that's been floating around here (I think I count myself as the 3rd or 4th? owner on BFC).

Mmmm...tasty. Very nice. My first carbon steel baby (5160) and it's got a completely different feel than any stainless I've handled. It's grabby and takes a sharp edge quick.

There's been two tiny pits in the front of the knife, and it SEEMS that some people have had luck here with preventing rust by applying a patina.

Well, so, I tried it. Cleaned the knife, dipped the blade in hot water, brushed some of my wife's lime juice on the front third.

BOOM. The thing goes BROWN, and SPOTTY. Well. That wasn't what I expected. Quick soak in baking soda, and break out the Flitz. Whew... nice and shiny again. Good as new.

Ack. So I try diluting the lime juice down about 1:1, and brush it on again. This time it's a little slower, but I never get it to turn greyish, and it's still kind of spotty and very uneven.

I ended up polishing it down again, applying a layer of FP-10 and then a coat of Tuf-Cloth.

So... is there a trick to this? And does patinizing the steel actually protect it any? Should it be turning grey instead of brown/rusty? Is there a way to get a slower but more even coat? Should I submerge the blade in the acid, instead of brushing it on?

Is this a stupid thing to do -- better to just keep it shiny and coated with Tuf-Cloth or Origins Ginger-Scented Body Oil?

Yikes.

-Jon
 
Rust can form on a blade in two basic ways, one is black and hard (called a patina), the other orange and soft. The orange version is bad as it breaks up the steel as it forms and it grows rapidly. The black form, while degrading the steel, isn't nearly as bad as the orange version and the black will prevent to some extent the orange rust from forming.

Some steels will take a patina quite rapidly, in all cases though you will see orange rust to some extent and the patina is not an even grey coat in any case. Unless you are very protective of carbon steel blades they will take a patina naturally. Though it will never take a smooth even finish as rusting is a random process.

In regards to corrosion protection, cleaning, drying and using a decent oil is a much better method.

-Cliff
 
Gun blue is great on 5160.. give it a try.. hint.. make sure the balde as well as the blueing stuff is warm, and have some water close to rinse it clean. It'll looks like hell the first few times, but try it a few times and you'll see.

A faster method is to dip it in ferric chloride. I use this to reveal temperlines or show the patterns in damascus. Ferric chloride is an acid, but it has one advantage to other acids (like the acid in the lemon), it doesn't create the ornage-brown rust which pits. it just makes it black. There are other acids which do this too, but most of them are pretty dangerous like sulpheric acid mixed with nitric acid ( I use that stuff to etch stainless damascus or to etch logo's).

You could try - for a do it yourself type a guy - to get a high a high pot or something in which you can boil water and dip the entire blade under, fill it with vinegar (potentially dilluted with water) and heat that. when that stuff is hot - it boils faster then water- take off the heat source and dip in the blade.. leave it sit and look what happens. When you pull it out, wash toroughly and rub with a cloth to remove excess rust.that creates a black patina too.
The dipping idea should work with lemon juice too, but you'll need a whole lot of lemon juice :D Rubbing a lemon is a bad idea.. almost always creates stots. If you wanna rub something, cut a fresh onion in half and use that, and keep rubbing untill you rinse the blade cleam.

With all these methods.. be carefull, these chemicals (besides the onion and lemons off course) are either dangerous or burning, and make sure there is absolutely no trace of grease, fingerprints or anything on the blade.

Hope this helps.. if you have more questions, mail me. I wrote down just about all method I can think of to patina a carbon steel blade.

Greetz and take care, bart.
 
OR
You could just routinley use the knife and the patina will develop on its own. It will take longer, but good things are worth waiting for :)
 
I have had pretty good success with vinegar, but it turns the blade a blackish color.

I have never found a way to quickly produce the beautiful, bluish-gray patina that develops naturally over time.
 
Thanks biogon, I've wanted to post this question for some time now. I read in one of Buzzbait's posts that he soaked one of his carbon blade knives in coffee and got a good patina. I tried it on an old timer 34OT. I soaked the clip and sheepfoot blade in coffee over night and I got an even smooth blue black patina on both blades. I had to soak them twice to get this. I left the spay blade to age naturally to compare. I've done the apple and onion thing but I feel I have more control with this method. I'll wait to see how the spay blade ages before doing any more.

Thanks Dean
 
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