Steel Question

[BigRed3588]

My dad had a knife made for me for my high school graduation and a few weeks after receiving it we noticed that there was some kind of black buildup on the blade. He took it back to the maker who cleaned it up, coated it in some kind of lubricant, and returned it. It has since been sitting in a safe for the past decade. I got to talking to my dad about it recently (I'm wanting to have a sheath made), and the issue of the blade's surface came up. Does anyone know what caused this and whether it can be fixed? My dad guessed that the maker used the wrong kind of steel or didn't temper it correctly, but we never got a concrete answer.

 

[M67]

Sounds like the blade developed a patina. Some steels do, some don't. Some people force patinas on knives to protect the blade from rusting easier or to make designs (mustard can do this)

 

[BigRed3588]

I looked up some photos and that is what the blade looked like. If I remember correctly, it developed within a month or so. Is it common for some steels to develop a patina that quickly? I always thought it took a fair amount of time. And is there anything that can be done to prevent it or am I better off just letting it happen? The knife has sentimental value so I just want to avoid damaging it.

 

[M67]

Depending on the carbon level, you can actually force a patina within an hour, maybe 30 minutes, using things with a higher acidity to them, like vinegar or mustard. If it patinas it helps against rusting, since the patina is like a forced rust (like gun bluing).

If you want to keep it shiny, use an oil and leave it coated. I use mineral oil. One of my friends who's into custom knives (damascus and others that have a lot of carbon) uses some type of wax, I forget the name of it.

I'm no knifemaker or knife expert (I just use them and spend too much on them) so I'm probably explaining the patina process at a way dumbed down level or "kinda maybe close but not quite" level.



Where's Brad when you need him?

 

[Bradsknives]

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M67 has it down.

All steels with High carbon will naturally form a patina over time if left untouched. You just need to decide how you want your blade to look. Keeping it shiny will require continued maintenance. After you have cleaned your blade (removing any contaminates), you can use Renaissance Wax on the blade for long term storage. A lot of people that use their knives will force a patina which creates an oxidation layer of the surface which will slow down or prevent the red/brown rust that causes pitting. Even with blades that have a patina, you will still want to wipe you blade down with an oil/ lube......Forcing a patina is not a 100% solution for preventing rust and corrosion.