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- Jun 11, 2012
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- 66
so i've heard the word patina a few times around here, but i don't know what it is. so what is it, and is it good or bad?
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what is patina?
- Thread starter outdoorsman196
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treeman8008
Banned
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- Jul 9, 2012
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- 73
it is a coating on your blade from use that forms on carbon steel. it isnt bad it prevents rust
To the best of my knowledge Patina is Iron (II) Oxide. Rust is Iron (III) Oxide
You can force a patina by using some form of acidic paste (mustard). The trick is to make sure that oxygen is not able to access the blade during the forcing process.
Iron (ii) Oxide is also known as black iron or black rust. If you've ever seen the water that comes out of a commercial fire sprinkler system, it is black. The colour is from black-iron rust, which forms in the absence of oxygen.
This is what patina looks like.
You can force a patina by using some form of acidic paste (mustard). The trick is to make sure that oxygen is not able to access the blade during the forcing process.
Iron (ii) Oxide is also known as black iron or black rust. If you've ever seen the water that comes out of a commercial fire sprinkler system, it is black. The colour is from black-iron rust, which forms in the absence of oxygen.
This is what patina looks like.
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Patina is another form of rust. Rust being the reaction of iron with water and oxygen to form iron oxide. The reaction is not as rapid, nor does it form pits nearly as quickly as the reaction which forms red rust as its product.
Red rust is Fe2O3, This one is what most folks consider as "rust"
Black rust is Fe2O4, This is the one that folks call "patina"
The black oxide layer that is formed is porous. When you oil the blade, the oil gets into the porosity and is held there. This means there is a thicker layer of oil than on a bare polished blade. The thicker oil layer then forms a better barrier to moisture and oxygen. This greatly reduces the rate of any corrosion reaction, but it particularly reduces the rate the red rust reaction, which requires more oxygen than the black rust reaction.
Red rust is Fe2O3, This one is what most folks consider as "rust"
Black rust is Fe2O4, This is the one that folks call "patina"
The black oxide layer that is formed is porous. When you oil the blade, the oil gets into the porosity and is held there. This means there is a thicker layer of oil than on a bare polished blade. The thicker oil layer then forms a better barrier to moisture and oxygen. This greatly reduces the rate of any corrosion reaction, but it particularly reduces the rate the red rust reaction, which requires more oxygen than the black rust reaction.
