Patina removal on M4 steel

Cornfed801

Cornfed801

Gold Member
Joined
Apr 19, 2021
Messages
333
Hey bladeforums I just picked up a Spyderco Advocate with some patina or spots on the blade. I would like to get it back to original somewhat. Does anyone have any tips of tricks on how to demo patina on M4 steel? I’m loving this knife but don’t love the spots on the blade.
 
Twindog said:
Be careful it's not pits. M4 likes to pit.
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Would that change what I use to clean the blade? Or if it’s pitted does that mean it won’t clean up? I live in Utah so I’ve never dealt with pitting or patina issues.
 
Cornfed801 said:
Would that change what I use to clean the blade? Or if it’s pitted does that mean it won’t clean up? I live in Utah so I’ve never dealt with pitting or patina issues.
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If it's pitting -- use a loupe -- it will be difficult to clean because the damage is below surface level. You can still do it, but it will take a different technique, such as a brush with metal polish. Someone will have a better suggestion.

The main thing it to prevent further corrosion. Still, CPM M4 is a great steel. I use it in the rainforest, but I have to be a lot more careful with it than I do with, say, Vanax.
 
Polishing will take a patina off, but if you have some corrosion which is deeper than the surface level, then you will have pitting and it can't be removed. Pitting is basically indentations in the surface of the metal formed by corrosion. When you remove the corrosion, it leaves a hollowed out space, or a "pit", which is another way of saying "hole". The corrosion has penetrated beyond the surface and formed a hole.

The only way to get rid of pitting is to resurface the blade, which will make it thinner, since you are forming a new surface by removing the old surface until you reach the same depth as the pitting.
 
Guy McVer said:
Polishing will take a patina off, but if you have some corrosion which is deeper than the surface level, then you will have pitting and it can't be removed. Pitting is basically indentations in the surface of the metal formed by corrosion. When you remove the corrosion, it leaves a hollowed out space, or a "pit", which is another way of saying "hole". The corrosion has penetrated beyond the surface and formed a hole.

The only way to get rid of pitting is to resurface the blade, which will make it thinner, since you are forming a new surface by removing the old surface until you reach the same depth as the pitting.
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Wow. Profound. :rolleyes:

 
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J. Doyle said:
Wow. Profound. :rolleyes:

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I'm so sorry to have annoyed you so much that you felt the need to be snarky about it.

My post obviously wasn't meant for you, so you could have just chosen not to respond.

Cornfed801 said:
Would that change what I use to clean the blade? Or if it’s pitted does that mean it won’t clean up? I live in Utah so I’ve never dealt with pitting or patina issues.
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^

One thing I have noticed on these forums is that many posters often have trouble understanding basic concepts, and they especially have trouble with being able to visualize things. So I often focus on trying to explain things in a simple and easy to understand way.

Ah but you're right. I was wrong for trying to be helpful. I won't do it again. I promise.
 
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