Spyderco Forums

Hi all,

I've greatly enjoyed having the Techno in my pocket, every single day, since the day I bought it 2yrs ago. I've used it extensively in the following contexts: cutting packaging, shaving aluminium, rope, string, various woods, plastic and (perhaps most relevant here), slicing food when hiking or shooting arrows.

However about a week after a recent trip, using the knife extensively across many cases and situations, I thought I'd give it another wash, only to notice that this time the marks just didn't come off. On close inspection, I see actual pitted marks in the supposedly oxide-resistant CTS-XHP steel.
Looking closely at the marks they even appear to be splash marks, or otherwise caused by a liquid of some sort. Does anyone have a clue as to what substance can do this to CTS-XHP? Trying to recall, I can only remember fruits as the only liquid-source the blade would've come in contact with, but perhaps there was a substance in some packaging I've overlooked.

A bit disappointed, to be honest, but eager to know what to look out for in future should I choose a knife with this steel again.

Cheers,

RemoteHost

Welcome to the forum,
Some fruits are very acidic, and will cause staining/patina on certain steels. I have not experienced this with CTS XHP but usually rinse my blades after use unless I'm trying to let a patina form as a sort of protection on certain steels like super blue, 52100.

Interesting, so perhaps it's kiwifruit or oranges then. I can't remember another fruit I would've cut in the past month. I guess with the blade already so messed up, I can test that theory without regret.

Also Flitz metal polish should remove those stains if they really bug you.

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.

I'd imagine it was due to slicing food while hiking and not getting all the food residue off in time.

In general when you cut up foods with your knife, especially acidic fruits like pineapples and oranges, you want to rinse them off with water as soon as possible. The longer it stays on the blade, the higher the risk of damage to the steel. This can also dull the edge of the knife.

H1 steel used by Spyderco is 100% rust proof. It is one of my favorite steels for hiking and camping for that reason. You can cut up some fruits with the knife, wipe it off, and never have to worry about rust. Take a look at the new Salt 2.

The longer you leave something corrosive on a blade, the more time it has to do damage. Compounding this are warm temps (body heat from carrying it) and evaporation (higher concentration)

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.

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.

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.

If it isn't brown then that will likely polish out. Without brown rust you usually do not have significant pitting. I have polished staining off of blades like that without issue. If you want to start simple then try toothpaste (not the gel but some gritty paste) and see how it works. That is very mild though and you may need to use something more aggressive. If you polish the entire blade the logos will get lighter but in my experience it takes quite a bit to completely remove them.

It is in some ways the amount of carbon vs the amount of chromium. XHP has fairly high carbon at 1.6%.

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)

sustratiotes wrote: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)

Ha! I prefer the term wabi-sabi, which loosely translates to "all things are impermanent and beauty is found in imperfection" https://en.wikipedia.org/wiki/Wabi-sabi

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

I don’t have Flitz down here either. Autosol might work, but it’ll change / polish the blade as well. I used ot for my VG10 that got a bit patina after peeling mangoes (wash immediately though :eek:) and it works albeit it also shines the blade a bit.

RemoteHost wrote: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.

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.

Hi to all, glad to be here :)

and

hi RemoteHost,

here you can find Flitz products...

lamnia (dot) com/de/suchen?s=flitz

I prefer a little polish on my blades.

Vivi wrote:I'd imagine it was due to slicing food while hiking and not getting all the food residue off in time.

In general when you cut up foods with your knife, especially acidic fruits like pineapples and oranges, you want to rinse them off with water as soon as possible. The longer it stays on the blade, the higher the risk of damage to the steel. This can also dull the edge of the knife.

H1 steel used by Spyderco is 100% rust proof. It is one of my favorite steels for hiking and camping for that reason. You can cut up some fruits with the knife, wipe it off, and never have to worry about rust. Take a look at the new Salt 2.

Good info, thanks a lot. I will check out the H1 line of Spyderco's. That Salt 2 looks like the everyday knife I need, in fact.