Boiling Becker Blades and Physics

[diced]

I was just pondering the physical attributes of knife steel. All steel is basically burning through an oxidation reduction reaction (at least at the molecular level). The rate at which it oxidizes is largely based on its components and the environmental factors (temp, humidity, pH level etc) .

Boiling or heating vinegar to achieve a patina is essentially introducing an acid (oxidizer) at a higher temperature to increase the rate of reaction on the surface of the steel. This type of patina apparently wears off easily based on posts on here.

A natural patina is more resilient and does not "wear off" easily in my experience. Is the difference a result of the natural patina being mainly introduced through the air and/or slower acting due to the more moderate acid exposure over a longer period?

Metallurgy confuses the hell out of me.

 

[Hunter Sharp]

This means what in English? We are just but simple folk! Lol JK no you make a good point and it makes sense. A forced patina is more so on the surface while a slow steady natural patina is embedded deeper in the steel... I think lol

 

[tradewater]

Not sure about that, but a good way to get a lasting patina is to plunge the blade into a fresh cow turd for a while. It won't wear off because you're a little hesitant to use it after that.

 

[SolidState]

As a professional solid-state chemist, I can tell you that you're on the right road, but nowhere near the destination. A patina is a coat of positively charged oxidized metal (cations) bound to another material (anions). Forced patinas use anions other than oxygen and hydroxide such as citrate, chloride, sulfide, sulfate or oxalate to form the patina. If you look at moh's hardness of different iron compounds such as ferric chloride or ferric citrate, they're not as hard as ferrous oxide or ferrous sulfide. Solubility also matters. Ferric oxide (orange rust) isn't really what you're going for either.

I guess what I'm saying is that it's not just pH and oxidation/reduction. It's how much something is being oxidized and by what. Vinegar is hydronium acetate (Acetic acid) which reacts with iron to produce Ferric acetate and hydrogen gas. Ferric acetate isn't anywhere near as hard as ferric sulfate, ferrous sulfide, ferric sulfate/sulfide or ferrous/ferric oxide/hydroxide.

Generally, you'll get the best coatings via anodization instead of heating. If done in dilute citric acid or vinegar, you'll generally get a rather robust coating. I make nanoelectronics and optics using this method.

 

[tradewater]

As a professional solid-state chemist, I can tell you that you're on the right road, but nowhere near the destination. A patina is a coat of positively charged oxidized metal (cations) bound to another material (anions). Forced patinas use anions other than oxygen and hydroxide such as citrate, chloride, sulfide, sulfate or oxalate to form the patina. If you look at moh's hardness of different iron compounds such as ferric chloride or ferric citrate, they're not as hard as ferrous oxide or ferrous sulfide. Solubility also matters. Ferric oxide (orange rust) isn't really what you're going for either.

I guess what I'm saying is that it's not just pH and oxidation/reduction. It's how much something is being oxidized and by what. Vinegar is hydronium acetate (Acetic acid) which reacts with iron to produce Ferric acetate and hydrogen gas. Ferric acetate isn't anywhere near as hard as ferric sulfate, ferrous sulfide, ferric sulfate/sulfide or ferrous/ferric oxide/hydroxide.

Generally, you'll get the best coatings via anodization instead of heating. If done in dilute citric acid or vinegar, you'll generally get a rather robust coating. I make nanoelectronics and optics using this method.

+1 :thumbup:

 

[Moosez45]

As a professional solid-state chemist, I can tell you that you're on the right road, but nowhere near the destination. A patina is a coat of positively charged oxidized metal (cations) bound to another material (anions). Forced patinas use anions other than oxygen and hydroxide such as citrate, chloride, sulfide, sulfate or oxalate to form the patina. If you look at moh's hardness of different iron compounds such as ferric chloride or ferric citrate, they're not as hard as ferrous oxide or ferrous sulfide. Solubility also matters. Ferric oxide (orange rust) isn't really what you're going for either.

I guess what I'm saying is that it's not just pH and oxidation/reduction. It's how much something is being oxidized and by what. Vinegar is hydronium acetate (Acetic acid) which reacts with iron to produce Ferric acetate and hydrogen gas. Ferric acetate isn't anywhere near as hard as ferric sulfate, ferrous sulfide, ferric sulfate/sulfide or ferrous/ferric oxide/hydroxide.

Generally, you'll get the best coatings via anodization instead of heating. If done in dilute citric acid or vinegar, you'll generally get a rather robust coating. I make nanoelectronics and optics using this method.

I was gonna post tha same thing, just not in such simple terms.

Moose

 

[Ethan Becker]

Hey Solidstate.....

Thankyou very much for that........Question....would chilling the knife in the acetic acid in the fridge somewhat like hard anodizing aluminum get a better coating ?.......Again....Thanks for your post......

Ethan

 

[TheWambo]

As a professional solid-state chemist, I can tell you that you're on the right road, but nowhere near the destination. A patina is a coat of positively charged oxidized metal (cations) bound to another material (anions). Forced patinas use anions other than oxygen and hydroxide such as citrate, chloride, sulfide, sulfate or oxalate to form the patina. If you look at moh's hardness of different iron compounds such as ferric chloride or ferric citrate, they're not as hard as ferrous oxide or ferrous sulfide. Solubility also matters. Ferric oxide (orange rust) isn't really what you're going for either.

I guess what I'm saying is that it's not just pH and oxidation/reduction. It's how much something is being oxidized and by what. Vinegar is hydronium acetate (Acetic acid) which reacts with iron to produce Ferric acetate and hydrogen gas. Ferric acetate isn't anywhere near as hard as ferric sulfate, ferrous sulfide, ferric sulfate/sulfide or ferrous/ferric oxide/hydroxide.

Generally, you'll get the best coatings via anodization instead of heating. If done in dilute citric acid or vinegar, you'll generally get a rather robust coating. I make nanoelectronics and optics using this method.

Thanks for the detailed explanation :thumbup: I think I got it after a few reads through and some googlein'

 

[diced]

As a professional solid-state chemist, I can tell you that you're on the right road, but nowhere near the destination. A patina is a coat of positively charged oxidized metal (cations) bound to another material (anions). Forced patinas use anions other than oxygen and hydroxide such as citrate, chloride, sulfide, sulfate or oxalate to form the patina. If you look at moh's hardness of different iron compounds such as ferric chloride or ferric citrate, they're not as hard as ferrous oxide or ferrous sulfide. Solubility also matters. Ferric oxide (orange rust) isn't really what you're going for either.

I guess what I'm saying is that it's not just pH and oxidation/reduction. It's how much something is being oxidized and by what. Vinegar is hydronium acetate (Acetic acid) which reacts with iron to produce Ferric acetate and hydrogen gas. Ferric acetate isn't anywhere near as hard as ferric sulfate, ferrous sulfide, ferric sulfate/sulfide or ferrous/ferric oxide/hydroxide.

Generally, you'll get the best coatings via anodization instead of heating. If done in dilute citric acid or vinegar, you'll generally get a rather robust coating. I make nanoelectronics and optics using this method.

Thanks SolidState, very informative. Would the patina that results from exposure to hydrogen sulfide gas cause the longer lasting patina? I was thinking about stripping a becker and stashing in spot that normally has low levels of H2S 2-20 ppm. I would check on it daily. Would this create a good patina or just orange rust?

 

[tradewater]

Thanks SolidState, very informative. Would the patina that results from exposure to hydrogen sulfide gas cause the longer lasting patina? I was thinking about stripping a becker and stashing in spot that normally has low levels of H2S 2-20 ppm. I would check on it daily. Would this cause a good patina?

At that concentration it would take a while. It would smell like rotten eggs forever though.

 

[NixKustoms]

As a professional solid-state chemist, I can tell you that you're on the right road, but nowhere near the destination. A patina is a coat of positively charged oxidized metal (cations) bound to another material (anions). Forced patinas use anions other than oxygen and hydroxide such as citrate, chloride, sulfide, sulfate or oxalate to form the patina. If you look at moh's hardness of different iron compounds such as ferric chloride or ferric citrate, they're not as hard as ferrous oxide or ferrous sulfide. Solubility also matters. Ferric oxide (orange rust) isn't really what you're going for either.

I guess what I'm saying is that it's not just pH and oxidation/reduction. It's how much something is being oxidized and by what. Vinegar is hydronium acetate (Acetic acid) which reacts with iron to produce Ferric acetate and hydrogen gas. Ferric acetate isn't anywhere near as hard as ferric sulfate, ferrous sulfide, ferric sulfate/sulfide or ferrous/ferric oxide/hydroxide.

Generally, you'll get the best coatings via anodization instead of heating. If done in dilute citric acid or vinegar, you'll generally get a rather robust coating. I make nanoelectronics and optics using this method.

I wanna see the patina on your knives!!!!!

 

[Eero]

Thanks for the posts guys. Very informative stuff. Most of it makes sense. To me the best way to understand all this stuff is to remember that the metal is alive and in a constant state of change morphing and reacting to the environment. I don't fight the rust fight with my 1095 I just kinda let happen what ever will on the surface of my BKs. I like the "natural" patina that happens. This thread needs pictures:

 

[1066vik]

a naturally occurring source for sulfides would be cutting up onion -- it's the sulfuric acid in the juice that makes your eyes water.
Sulfuric acid is also used in some drain cleaners -- but you want to be careful with it, since it can pit a blade pretty fast.

 

[zpstl321]

An onion pattern on the blade would look kind of cool. I have other 1095 blades that I more or less polished abotu 2 years ago and they still have not rusted. They don't get used every day though.

 

[diced]

I might give it a try, the levels are high enough in the area that it will turn a penny green in about a week, it wont leave any odor on it. The rotten egg odor from in H2S is a good thing, when you stop smelling it you could have some problems (it paralyzes the sense of smell at levels approaching a fatal exposure). I just don't want to ruin a knife trying to achieve a patina. I have never really modded a knife for aesthetics, but after seeing some of the work on here it looks like it could be some fun projects for the winter. Like the looks of that BK2 above, I guess I should just use them more, but usually end up using smaller blades for most knife tasks I have. Liking the 24 though its a pretty hue already.

 

[Hunter Sharp]

I heard that the best way to force a patina is by using Chuck Norris spit, but you have to be very careful not to get it on anything but the blade! Beckers are the only thing tuff enough to handle that kind of torture

 

[pap11y]

Not sure about that, but a good way to get a lasting patina is to plunge the blade into a fresh cow turd for a while. It won't wear off because you're a little hesitant to use it after that.

That made me laugh loudly at work..