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Thread: Does a patina help prevent rust? How much protection?

  1. #1
    Spyderco Forum Registered User jackknifeh's Avatar
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    Does a patina help prevent rust? How much protection?

    I've always read that a patina forming on carbon blade steels is a protective coating against other types of corrosion. I know almost nothing about corrosion. Actually rust is the only work I think I've ever used referring to corrosion until I heard of patina. My question is how much protection does a patina provide?

    Example: I disassembled my Bradley Folder and forced a patina on the entire blade including tang. This of course means inside the hole, around the tang, everywhere seen and not seen when the knife is assembled. So, if the patina protects the steel, how much protection is there? Can the amount of protection be measured? I've always assumed we should also do whatever we would normally do to fight rust. If my M4 blade has a patina on the tang can I stop using tuf-glide as a corrosion fighter and only concern myself with lubrication?

    Anybody know about this? I want my grandson to enjoy my knives so I'll continue doing whatever I can to protect them. So I guess this question is mainly out of curiousity. Or, with a patina on the blade and tang both, can I do nothing else to fight corrosion and use the GB every day on a salt water fishing boat?


    Jack

    My EDC for a while. Stretch with carbon fiber handle, Chaparral 2, Dragonfly 2 with kirinite MOP handle, Manbug with bolster/red bone handle. Super blue/420J1 blades on all three (except Chaparral).

  2. #2
    Spyderco Forum Registered User shunsui's Avatar
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    I forced a patina on my superblue Endura. Didn't look very interesting, but it does seems to protect the steel a bit. I've been perversely using the knife for EDC for a month or two and haven't had any problems with rusting despite the fact I use no oil or other type of protection. I've been daring it to rust and so far it hasn't.

    I'd recommend a Pacific Salt for that salt water fishing boat though.

  3. #3
    Spyderco Forum Registered User kbuzbee's Avatar
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    My experience, Jack, is it does pretty well. My understanding of patina is it occupies the iron with O3 preventing attack by O2 (maybe those are reversed? Or maybe more complex - Fe2O3 vs Fe3O4? Something along those lines)

    Anyway, all my kitchen knives are carbon steel. They all have a nice patina and, if I wipe them down after use, no rust issues. I did use a carbonne Opinel paring knife on a lemon and failed to wipe it down immediately. It didn't rust but it made a very black spot in the already grey steel. So my guess is it's some protection, but there are limits.

    I do still tuf glide my pivots even if they have a patina. Seems like good insurance for an area you can't easy see or wipe down after use.

    Ken
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    Spyderco Forum Registered User yablanowitz's Avatar
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    Patina is "rust". It is a black oxide which adheres tightly rather than a red oxide which flakes away, but it is the same compound, just like martensitic and austenetic steel. It protects the underlying steel from further oxidation by keeping oxidizers away, but that protection is not absolute. How much protection it will provide depends on a host of variables, most of which are beyond your control. If you want to hand your blades down, use them as if they were glass and care for them as if they were your children. Or better yet, coat them with Cosmoline, wrap them with waxed paper and lock them in a climate controlled vault. Or you could use them as the tools they are, wipe them down after use, oil the joints once in a while and hand down a memory of all the things you've done with it.
    I don't believe in safe queens, only in pre-need replacements.

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    Spyderco Forum Registered User jackknifeh's Avatar
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    Quote Originally Posted by yablanowitz View Post
    Patina is "rust". It is a black oxide which adheres tightly rather than a red oxide which flakes away, but it is the same compound, just like martensitic and austenetic steel. It protects the underlying steel from further oxidation by keeping oxidizers away, but that protection is not absolute. How much protection it will provide depends on a host of variables, most of which are beyond your control. If you want to hand your blades down, use them as if they were glass and care for them as if they were your children. Or better yet, coat them with Cosmoline, wrap them with waxed paper and lock them in a climate controlled vault. Or you could use them as the tools they are, wipe them down after use, oil the joints once in a while and hand down a memory of all the things you've done with it.
    The last option is what I would value.

    My EDC for a while. Stretch with carbon fiber handle, Chaparral 2, Dragonfly 2 with kirinite MOP handle, Manbug with bolster/red bone handle. Super blue/420J1 blades on all three (except Chaparral).

  6. #6
    Spyderco Forum Registered User yablanowitz's Avatar
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    Exactly. A few pits won't keep a knife from cutting, so why worry about them? Handing down a pristine beauty is okay if you are a museum curator, but handing down a worn rusted but still tight and sharp companion is far more satisfying to me.

    I don't believe in safe queens, only in pre-need replacements.

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    Spyderco Forum Registered User SpyderNut's Avatar
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    Hey Yab, is that a Schrade model 34OT? Appears to be one of the earlier models due to being made in NY USA. Have a few of those myself. Good little knives, although they do have a penchant for rust.
    Michael

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  8. #8
    Spyderco Forum Registered User jackknifeh's Avatar
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    Quote Originally Posted by yablanowitz View Post
    Exactly. A few pits won't keep a knife from cutting, so why worry about them? Handing down a pristine beauty is okay if you are a museum curator, but handing down a worn rusted but still tight and sharp companion is far more satisfying to me.

    Quote Originally Posted by SpyderNut View Post
    Hey Yab, is that a Schrade model 34OT? Appears to be one of the earlier models due to being made in NY USA. Have a few of those myself. Good little knives, although they do have a penchant for rust.
    When I saw that picture I thought "HEY, how did you get the knife I had when I was a kid?" That is the exact model I remember when I think of the pocket knife my Dad gave me when I was 10-12 years old. Don't remember the Manufacturer I had but it was definately a Stockman.

    My EDC for a while. Stretch with carbon fiber handle, Chaparral 2, Dragonfly 2 with kirinite MOP handle, Manbug with bolster/red bone handle. Super blue/420J1 blades on all three (except Chaparral).

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    Spyderco Forum Registered User yablanowitz's Avatar
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    That's my old reliable 8OT stockman, the next size up from the 34OT. Still tight and sharp after 40 years in spite of some rust. Word of advice, don't carry a carbon steel pocketknife when you repair and adjust lawn sprinkler systems for a living.
    I don't believe in safe queens, only in pre-need replacements.

  10. #10
    Spyderco Forum Registered User SpyderNut's Avatar
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    Quote Originally Posted by yablanowitz View Post
    That's my old reliable 8OT stockman, the next size up from the 34OT. Still tight and sharp after 40 years in spite of some rust. Word of advice, don't carry a carbon steel pocketknife when you repair and adjust lawn sprinkler systems for a living.
    True that.
    Michael

    Live as if you were to die tomorrow. Learn as if you were to live forever.
    Mahatma Gandhi

  11. #11
    Spyderco Forum Registered User Evil D's Avatar
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    Jack my M4 Manix 2 has a forced patina AND Tuff-Glide on it, and it still has spot rust forming. Basically like everyone said, screw it. Keep a healthy dose of TG in the pivot, and roll with it. There are slipjoints that are 100 years old with 100 years of pitting on them that are still great users, and as long as the pivot doesn't form a bunch of rust and pitting to the point that the action is compromised, it just adds character IMO. I happen to think a pitted/patina'ed/polish worn finish is very attractive. This box knife I've carried for 14 years has rusted and then been polished from wear and being in my pocket. If there were a way I could reproduce this on a knife blade, I would do it in a heartbeat.




    That kind of finish with a polished edge would look gorgeous IMO. I suppose you could just allow a blade to form a layer of light rust and then polish it out and treat the steel so it doesn't rust any further.

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    Spyderco Forum Registered User jackknifeh's Avatar
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    Quote Originally Posted by Evil D View Post
    Jack my M4 Manix 2 has a forced patina AND Tuff-Glide on it, and it still has spot rust forming. Basically like everyone said, screw it. Keep a healthy dose of TG in the pivot, and roll with it. There are slipjoints that are 100 years old with 100 years of pitting on them that are still great users, and as long as the pivot doesn't form a bunch of rust and pitting to the point that the action is compromised, it just adds character IMO. I happen to think a pitted/patina'ed/polish worn finish is very attractive. This box knife I've carried for 14 years has rusted and then been polished from wear and being in my pocket. If there were a way I could reproduce this on a knife blade, I would do it in a heartbeat.




    That kind of finish with a polished edge would look gorgeous IMO. I suppose you could just allow a blade to form a layer of light rust and then polish it out and treat the steel so it doesn't rust any further.
    Possibly the best description of how to think about user knives I've heard.

    Anyway, I may continue to post a thought or pic when it seems on subject in this thread. So, here is a picture of my Stretch after I blasted the SB area with turpentine a day or two ago. Then I polished the edge bevel with a strop removing the patina. The bevel is very shiny like a scratchy mirror under 10x magnification. Then I have kept it treated with tuf-glide. I'm going to see how it does under normal use instead of drowning the blade in a patina forcing liquid. I cut a hot dog up tonight and wiped the blade off within 2 minutes. The edge bevel is still shiny with no hint of patina.


    The hot dog had ketchup and cheese on it. I know, I'm a gormet. The first time I used the blade on food I had used a very old cloth that may have been dead. Don't know for sure. Patina formed after cutting food. This time I used a new, very wet cloth. Let the blade dry then wiped the blade off using 91% alcohol. No patina after cutting hot dog. So, for an accurate opinion of the war between patina forming against tuf-glide lots more controlled, repeated tests are needed. I will not do them. I will probably post anything half-way interesting but the info will come from every day knife use. I'll routinely maintain my knives and use them how I want and whatever will be will be (as the great Doris Day said about a million times ).

    Jack
    Post edit: Replace any "turpentine" with "vinegar".

    My EDC for a while. Stretch with carbon fiber handle, Chaparral 2, Dragonfly 2 with kirinite MOP handle, Manbug with bolster/red bone handle. Super blue/420J1 blades on all three (except Chaparral).

  13. #13
    Spyderco Forum Registered User
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    Jack.

    In my non scientific experience, polish will help delay patina/rust to develop. On my M4 Bradley and E4 SB.

    However I'm also a strop nuts that strop my blade as and when I feel like it soitmightnotworthanythingactually.

  14. #14
    Spyderco Forum Registered User The Deacon's Avatar
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    Quote Originally Posted by jackknifeh View Post
    I've always assumed we should also do whatever we would normally do to fight rust. If my M4 blade has a patina on the tang can I stop using tuf-glide as a corrosion fighter and only concern myself with lubrication?

    Anybody know about this? I want my grandson to enjoy my knives so I'll continue doing whatever I can to protect them. So I guess this question is mainly out of curiousity. Or, with a patina on the blade and tang both, can I do nothing else to fight corrosion and use the GB every day on a salt water fishing boat?


    Jack
    I'd suggest treating a carbon steel blade with a patina at least as well as you would treat a blued, non-stainless steel, firearm. I don't know about you, but I would not carry one of those daily on a fishing boat without additional rust protection.
    Paul
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    Spyderco Forum Registered User jmh58's Avatar
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    Quote Originally Posted by jackknifeh View Post
    The last option is what I would value.

    YEP!! Tools.. NOT jewels!!! John
    A great rabbit chase ends with a.. BANG!!!

    Never too old to relive your youth!!

    Life is to short to carry a cheap knife!!!

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