CPM-3V Rust test

[MacTech]

Butch kindly sent me an Atwood Prybaby clone in CPM-3V to put in the fog chamber for testing


the obligatory "Before" picture
test started at 7:30 PM EST 10/11/06

[Zac]

horray!!!!!1111 :D

[rcbalt2]

This should be an interesting test. I know next to nothing about 3v.

[Jerry Hossom]

You may or may not be able to draw meaningful conclusions from this. 3V's corrosion resistance depends somewhat on how it was heat treated and how it is finished. To some extent it may also depend on when it was made. Recent (last couple years) batches have had less/fewer oxide contaminants that are usually the focus for corrosion to begin. You'll see orange spots where those are on the surface. I'll be interested in the results.

I normally ferric chloride etch my 3V blades which seems to make the steel less prone to corrosion. (I also like the patina it gets after etching.)

[MacTech]

11:30 PM, a verrry faint patina of rust is forming, i'll give it a few more hours to be sure, but it's already showing signs of rusting

from 7:30 when the test started to 11:30 for the first faint signs of rust, 3V's not doing too well, 5 hours to start rusting.....

if by tomorrow i get actual rust, i'll pull the prybar out, dry it off, then resurface it with the wire wheel on my Black&Decker Dremel clone and retest it

i just realized i'm seeing some slight oxidation patches on the "before" pic, so the first test may not be valid, ahh what the heck, i'll dremel clean one side and leave the other side stock now....

[butch]

you would post a picture of the little test marking kit i tried but that looks goofy :o cant wait till you rust that little part off
also did you see the little crack in the prying arm quenching faster is not always better im just glad this was the first 3v i had heat treated ( i new better then to try something like that with a blade and that just proved it)
thanks again for testing this since you have a handfull of different steels to campare it to
and for anyone watching this just please remember its not a stainless steel but the etching should help im crossing my fingers
butch

[MacTech]

Okay, here's the cleaned-up topside of the prybar;


just to give you an idea of how reactive our air is here, i had just polished the topside of the prybar when i noticed it was already starting to dull

on top of that, we have a major storm blowing in tonight, should make our air supersaturated with moisture....

[butch]

You may or may not be able to draw meaningful conclusions from this. 3V's corrosion resistance depends somewhat on how it was heat treated and how it is finished. To some extent it may also depend on when it was made. Recent (last couple years) batches have had less/fewer oxide contaminants that are usually the focus for corrosion to begin. You'll see orange spots where those are on the surface. I'll be interested in the results.

I normally ferric chloride etch my 3V blades which seems to make the steel less prone to corrosion. (I also like the patina it gets after etching.)

got the bar 05/04/05 heat P68848-3-68-1 heat treat was preheat 1550 hold 7 min 2000 hold 30 min was air quench ti ll i thought it was not cooling fast
gasp interupted water quench :o
i now have quench plates
i didnt have Ln at the time so it was tempered 3 times 1000 2 hours each it was more test that i had planed on braking but after hitting it with a hamer a few times and didnt brake i said the **** with it and kept it as a bottle opener

i to like the nice grey etching gets me

[Jerry Hossom]

It really needs to get from high heat to under 1000F in about a minute or less or it won't fully harden. That's one of the reasons 3V got mixed reviews when it first came out - before quench plates. I don't know what effect that might have on corrosion resistance.

[MacTech]

Prybar placed back in the tank at 11:40 PM, at 1:20 AM there is now rust spotting on the cleaned side, coated side no major changes, rust started in a little under 2 hours....

[butch]

is the rus sorta like light pitting because i have noticed that when it rusted for me that it was always in the same spots the odd pits
is this what your finding also
the pits btw were not there when i etched the part it was only after the first bits of rust from being in the hot tub one night

[Jerry Hossom]

Those isloated spots/pits are the oxide contaminents. Usually by the time you see one, there is a pit under it.

[butch]

going to have to call back the other knife from that bar and have a look
not a big deal the guy that has it said the unit came down with a no blade over 3 inch for going to the sand box im not sure how i would feel about that but so be it
that bar was 2 knives and that atwood clone one knife is in the shop for me so i know where all the steel got to
Mr Hossom you made me go back to my log book to look all that up last night to make sure i didnt have to call more back
cant learn without keeping track of what you did right BTW the knife that im calling back has been used for over a year with no reported problems i just ahve to make sure
butch

[CKE]

I have yet to be able to get rust on my Krein Micro Chef in 3V. Cutting everything acidic in sight still has not had any effect on it. I really like 3V for its edge holding and ease of sharpening. Spyderco should definetly make some use of it.

Craig

[MacTech]

8:05 PM 10/12/06 pics;





i guess it's safe to say the bar has failed at this point, i'll leave it in until tomorrow evening see how much more the rust grows

[Jerry Hossom]

3V is my favorite steel, bar none. It's toughness is remarkable. The edge it takes is amazing. I have had no problem with 3V rusting outside of the testing I've done and once when I left a blade in a moist environment for a couple months. Even then, the problem was confined to about 5 spots in one area of the blade.

I think a lot depends on the finish, but that's true of any steel. The finer the finish the less corrosion. Lots of variables...

Edited to add:

On that pic, notice that the brighter (better finished) side showed substantially less rust.

[Zac]

While it looks bad, I am guessing it is just the very surface layer. Also, your corrosion machine is just that. I am going to give AUS-6 about 24-48 hours.

[butch]

thats about how it looked when it sat in the bed of my truck for a few weeks it real didnt look to rust alot more then that
also i forgot to note that the test steel never had a coat of oil of marine tuff coat while i had it
perhaps i should get a 2nd bar sample i do have another cut off that i could use if down the road you want to try a few more steels i ll make a few plates
i ll redo the 3v
make a 10v
and i have cpm154 that i have extra of
they will just have to wait till i do a firing of that type steel again
let me know

[jaislandboy]

thanks for the thread Mactech! you're our go to guy for Corrosion Testing...! it's been a very educational read....esp. with Mr Hossom chiming in! Welcome to the Spyderville.......I'm enjoying my fistful of Retribution2! :cool:

[Jerry Hossom]

Butch, is that the same piece that had already rusted in your truck? If so the micropits from the previous rusting would accelerate it rusting again, because water would immediately collect in those pits. Of course if you ground all that off it wouldn't matter. That and the better finish may explain the brighter side rusting much less than the other.

Zac, that is probably not just surface rust though it hasn't been rusting long enough to pit very deeply. Almost every rust spot I've found on 3V (having rusted much longer than this piece) had a pit beneath it. That's why I asked about the previous rust on this piece. Steel surfaces and edges are all about microstructure IMO. Long before you can see anything there are very minute areas of corrosion, pitting, cracking and chipping, eventually these things manifest themselves as bigger problems. The more effort put into refining the microstructure with better finishes, the less these problems occur.

All that said, 3V is not stainless and shouldn't be treated as such. In my experience it's about the same as D2 in that regard. I sort of look at it as a beautiful woman with a wart on her nose. You have to look past that to see what's important.

Thanks, Brian, it's nice to be here.