Passivate CPM3V ?

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Tom, do you also passivate your CPM3V to help protect against rust ?
Jerry Hossom seems to do this with this steel.

Just wondering, as personally i don't have any problems in that area with my Dingo.
But i take care of of the knife after using it, so it probably won't develop that quickly.
 
Sorry to reveal my ignorance but, I have no idea what passivate means? Can you explain?

Tom
 
Tom Krein said:
Sorry to reveal my ignorance but, I have no idea what passivate means? Can you explain?

Tom
Click to expand...

He's talking about etching the blade in FeCl. There was thread on the Spyderco forums a while back where this was mentioned.
 
Yes, he is. :D

The problem with corrosion on 3V is the presence of oxides in the steel at the surface. It's a product of the production process and is what makes the steel susceptible to the rust spots/pitting that can happen. By etching the steel, I remove those oxides and even though the patina in many circumstances might increase susceptibility to corrorion, it doesn't in this case, possibly because I brush the steel back to a fine finish after etching.

Edited to add: Sorry Tom, I didn't notice that this was your and Dan's forum. I followed a link and didn't read the banner. Didn't mean to intrude.
 
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Jerry, GLAD to see you respond. Feel free to share all the info you like! Knowledge is never a bad thing!

Dan is no longer part of K-9 Knives. We split on good terms, he was just too busy with his knives and teaching.

Tom
 
Wait a minute !
There is a standard industry term "passivation" for stainless steel. This is a process where the stainless steel is treated with acid. This removes foreign material from the surface and increases the thickness of the protective oxide surface layer [chromium oxide]. Foreign material such as particles of carbon steel on the surface will rust and the rusting will continue into the stainless ! Don't use the term for other things.
I'm not sure what Jerry accomplishes . Oxides are normally protective ,in fact the 'patina' is nothing more than oxide.What say Jerry ??
 
I don't think I'm using it for "other things". While 3V is certainly not stainless, it does contain enough free chromium to provide some anti-corrosion protection. When I first used the steel and noted how it corroded, widely scattered spots of orange rust under which were fairly deep pits, I ask the then chief metallurgist at Crucible Steel about what I saw. He said the spots were the result of surface oxides, presummably iron oxides. I'm guessing these oxides are contaminents in the CPM powders which are then trapped in the steel when it is hipped. With that in mind, I reasoned that I could remove those particular oxides with an acid bath. Whether the reasoning is correct or not, it worked and I've seen a much reduced tendancy for 3V to corrode after "passivation". Whether it is the formation of Chromium oxides from the free chrome or simply removal of the problematic iron oxides, I really don't know.

Robert, you know I'm a technical heretic, but I really do try to make things better than I found them. :)

I now "passivate" all the steels I use, CPM-3V, CPM-154 and S30V. I like the patina that's formed and whatever else it does is like chicken soup, can't hurt. :D
 
If it works it works.But I'd rather you use a different term than passivate, perhaps acid cleaned .
 
Not to jump in but I think Jerry was correct using passivate. I know that Busse also recommends cleaning off the oxide layer on the new line of unfinished knives. INFI is very rust resistant, but for some reason the oxide layer that is left is VERY prone to rusting. Look into it, I guess depending on the circumstances oxides can be detrimental. I would also wager that to passivate is to apply a process, not just specific to stainless steel. . .
 
Jerry, would you have any pictures of the passivated CPM 3V on your work? Can you polish/blast it afterward or would this ruin the effect?

Thanks for taking the time to post this info!

I am always trying to learn how to make my knives better!

Tom
 
If you do anything that removes the etched surface, you are back at square one. I take the blade to a bright brushed finish, etch, then brush it out again to remove the loose oxides from the surface. You can use fine scotchbrite for the last part. I think it's important to get a fine finish before etching though or you'll create more corrosion problems than you solve.

Here's a pic of a small utility knife in 3V with the etched finish. Not really much to see, just a little darker than a non-etched surface.
 
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Passivate from Merriam Webster

"to make inactive or less reactive <passivate the surface of steel by chemical treatment"
 
"really not much to see " especially since you don't post the photo !!
 
I think maybe you left the knife in the picture in too long... it disappeared :)

No pics...

Tom
 
Similar, but in CPM-154. I rarely make two the same, especially when I'm fussing with getting a design just so.
 
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