What caused these permanent stains/etches on my CTS-XHP steel Spyderco Techno?

[RemoteHost]

If a steel has iron in it, it is not stainless, only stain-resistant. Stain-resistance is a matter of degree and varies with the kind of iron-based steel. M4 is not as resistant as XHP.

The staining on your Techno does surprise me. The pattern suggests you put the blade away wet and gave the corrosive agent time to do its thing.

When manufacturers boast their blades are "stainless" or, more honestly, stain-resistant (H1 and LC200N excepted), I think they assume blades will be cleaned when work is done.

None of my XHP or other stain-resistant blades has hinted a stain, But I do rinse and dry them, chiefly, however, for hygiene as I often pull my knife for food-prep.

Fair call. I'll definitely be more vigilant about cleaning after cutting acidic material - admittedly I didn't consciously have fruit in mind as being a potential oxidant until the responses to this thread. Guess the knives I grew up with as a kid were of quite a different blade steel composition!

[RemoteHost]

Don't bother trying to polish out the stains or pitting unless your intent is to remove the original finish on the entire blade - which includes the original laser etching as well. The natural tendency is to use less polishing effort on the factory markings, the end result just making it obvious that a restoration attempt was made. If it were mine, I'd value it as a useful tool that had served well. Think of it too as something you can actually show people to prove that the "stainlessness" of most stainless steels is relative, not absolute.

True, it certainly does bear its scars now! I guess I'll have to find a way to value it in that sense now. I agree it'd be pointless to try to polish out the 'etching', would obviously appear to be a case of its owner trying to pretend it didn't happen ;-)

[RemoteHost]

Free Cr% is what needed for passivation/resist against corrosion. XHP's has about 7.5 freeCr% post-ht according to calculation from my-ht formula (I've no idea how Spyderco ht their but should somewhere in the ball park). IME - this translated to around 8-10% better corrosion resistant than ~7.5freeCr% 3V/Cruwear, etc... 8-10% because CrC (chromium carbide) does resist corrosion if passivated (depend on external chems & thermal & electrical current if any).

There are spots on edge bevel of your blade - hence, patina (oxidation) occurred. Regular stains and very shallow oxidation can be remove with oxalic acid (such product as bar-keepers-friend, just don't soak too long - acid can etch your blade).

It is easy for many to assume/project XHP 16%Cr in composition as all goes toward passivation/corrosion-resistant. Only freeCr% after hardened state is what count.

Sounds like you know your steel... Interesting just ~8% is enough to open up the possibility for a range of oxidation 'threats'. Indeed, perhaps I'm overreaching calling the scarring 'etching' and that they are just shallow patina marks as you suggest. Makes me think that it'd be good to get under my 400x microscope. Can also just try the oxalic acidic approach on a spot of the edge, as a test too. Will look it up when back from this trip.

Many thanks for the detailed reply

[RemoteHost]

beausage

"Beauty by usage. Beausage sounds French but it's not; instead it's a synthetic combination of the words beauty and usage, and describes the beauty that comes with using something."
(http://www.urbandictionary.com/define.php?term=Beausage)

Hah, nice. Will adopt this word. Cheers.

[RemoteHost]

RemoteHost, is it possible you used a sharpener on a carbon/alloy or tool steel blade then used it on the XHP knife? Putting carbon steel powder on a stainless knife can jumpstart the rust process and have it look similar to yours. Just a guess.

Bluntcut, thanks for the explanation of Free Chrome and keeping it at my level and understandable. :)

Joe

Interesting.. The only thing close to that would be dust from cutting my carbon-fibre arrow shafts (with an edged file).This knife has definitely been exposed to such dust - in fact I even used it to quickly cut the tip off a broken arrow (that I wanted to keep) around the time it would've got those marks. Hmm.. Wish I had a lump of XHP around to test.

[RemoteHost]

You can actually get Flitz in Germany, but it's going to be expensive, not really worth it. Just get some Gundel-Putz polishing paste, it's just as good.

Danke! Ich werde suche und testen.

[nicked.onaut]

Thanks, albeit not sure that brand exists here in Germany. Nonetheless, the 'etches' are deep enough to be easily felt dragging fingernails over them, so I wonder if polish of any sort would work at all. I'll try a polish or two and report back after this trip in a few days.

Interesting, I always thought Flitz was a German brand. Turns out to be a Wisconsin USA brand, made from German ingredients. If you cannot find Flitz, Simichrome might work as well.

From the pattern of the streaks and blotches on the blade and the history you relate, the marks are most likely due to some orange juice residue over time, and carrying such in a "sweat-moist environment" would augment the slow oxidation.

You could polish out as much or as little as you wish on a trial and adjust basis.
A scale of mild-to-more-aggressive would be:
--Case polish
--Flitz = +/-Simichrome; Flitz seems to have a bit more chemical effect, but they're often a tossup
--Mother's Mag and aluminum polish (this will almost always get more of what Flitz/Simi left behind)

--a regular ink eraser, or
Rust eraser; with these, and anything below, be careful to rub parallel to the original grind lines

--Bronze wool or SS wool, 000 or 0000, with some light oil/solvent
regular steel wool can leave tiny particles behind, which can subsequently rust; not so the Bronze and SS wool, which also are softer than the steel itself but not the oxidation. Proof is in the pudding. YMMV etc

There are other agents one can use (chem/ rust removers/oxalic acid etc) but they tend to have potentially more risk then warranted for this need.


Interesting "new" history about Flitz, as I have used it for at least 35 years and have paid no attention to the company changes.
I first encountered Flitz at a show with a friend in the early 80s (around the time he had three retail establishments which added Spyderco to their other wares). The charming and enthusiastic young man with whom I spoke was Ulrich (we were young, then) and he chuckled at my DLI-augmented college German.

Even decades old Flitz works fine. Here are two tubes of different vintage. The lower is older, from about 1984 or '85 based on the kit box from which i pulled it, and the upper is newer (note the label /marketing change).

Both were obviously made prior to 1990.

The manufactured product was *packaged* in Wisconsin, USA.

(I'm pretty sure I have an older tube, in a ranch box, but I won't be up there for a good while. En cose some newer product, too..)

From Dun and Brandstreet I see that they incorporated and began *manufacturing* in the US, in Waterford WI in 2002. Even that date seems like only yesterday.










Here's a pic from a show long ago which includes their poster and WI location (from Flitz' own history files)



Good luck

nicked.onaut

[nicked.onaut]

Just to clarify, they previously imported product, which was then packaged in the US, then began manufacturing product in the US from ingredients imported from Germany (I think starting in 2002, quick a.m. phone call is in order...)

[JRinFL]

Just to clarify, they previously imported product, which was then packaged in the US, then began manufacturing product in the US from ingredients imported from Germany (I think starting in 2002, quick a.m. phone call is in order...)

Thank you. I thought my memory had failed me, but I did remember it correctly being made in Germany (at the time) at least.

[DougC-3]

Thanks to all the above contributors. I love information! Also, digression "is the better part of valor," not disgression

Also, getting back to the beauty or ugliness of patina:

Ha! I prefer the term wabi-sabi, which loosely translates to "all things are impermanent and beauty is found in imperfection"

“There is no exquisite beauty… without some strangeness in the proportion.” ― Edgar Allan Poe

[awa54]

You could also just cut a !of of cardboard with it... That would blend and remove the etched spots replacing them with usage marks :D