Darkening Stainless Steels

[timogranzotti]

I've used ferric choride on hardened 440A and a benchmade pocket clip, which I'm assuming was 420j2 or 300 series. In both cases the ferric gave both a dark matte finish alot like black phosphate in appearance. I actually let the benchmade clip soak for a while and it came out looking like a rough blackened beadblast. Can't remember the concentrations I used but I think the clip was something like 50/50.

Would 440C have the same results? I dunno...

 

[timogranzotti]

I dug up this old thread on what I did.

Corrosion has not been a problem with either knife. The Mora even survived several weeks living outside in my back yard getting a nightly spray from the sprinkler with no corrosion at all.

Shecky, I did a little research on whether the application of naval jelly would compromise the steel's integrity and I found that stainless contains chromium which makes it stainless:

"a minimum of 13% (by weight) chromium, and up to 26% is used for harsh environments.The chromium forms a passivation layer of chromium oxide (Cr2O3) when exposed to oxygen. The layer is too thin to be visible, which means that the metal remains lustrous. It is, however, impervious to water and air, protecting the metal beneath. Also, this layer quickly reforms when the surface is scratched. This phenomenon is called passivation and is seen in other metals, such as aluminium and titanium. When stainless steel parts such as nuts and bolts are forced together, the oxide layer can be scraped off causing the parts to weld together."

So it it possible it still contains all the 'stainless' aspects as it did before, with the surface still coated by the chromium and invisible, showing only the change in the metal beneath from etching...

 

[SaMX]

naval jelly sounds cool, I might have to try that on some pocket clips. I hate when a black pocket clip get the paint chipped off around the edges. I 'd like to just sand off all the paint and etch them.

will the naval jelly take off the paint too?

maybe I can just soak it in coke

 

[shecky]

IIRC, stainless Moras are around Rc 57-58.

I didn't expect the knife to undergo significant corrosion as a result or etching. Particularly with the 12C27mod used on that knife. It didn't keep folks from warning me, however. Interestingly, the knife was also tested along a Meyerco blade in unetched 420j2, which is supposed to have particularly corrosion resistant properties. Yet it suffered from significant surface rust in the backyard test! Go figure.

 

[knarfeng]

I recently ordered a Predator WSK and was searching for methods of darkening the 440C Stainless Steel blade. I was looking for a method or acid that would be
the least toxic as I will be also using the knife for gutting, skinning, etc. but durable enough for heavy chopping, drawing, etc. Any Ideas? Thanx!

Several folks have reported good results with this kit:
http://www.caswellplating.com/kits/black.htm#stainless

They make another kit for non-stainless.
I cannot speak from personal experience as I do not like darkened blades on my knives.

Here is my answer from your other thread. I stand by it.

 

[yoda4561]

Would 440C have the same results? I dunno...

I'd bet on it being even faster. I'd check but I don't have any users in 440C that I could play with like that, closest I have is 420HC from buck an an ATS-34 BM 710.

 

[timogranzotti]

Here is my answer from your other thread. I stand by it.

Thanx, black oxide at room temp. seems to be the ticket. Easy, cheap too. Have a few questions regarding the product; if it''ll affect the corrosive resistances, how long it'll last, if it's safe for stainless steel meant to cut food as well...I'll contact them...Thanx again.

 

[SaMX]

I'm not sure that etching with naval jelly would compromise the corrosion resistance, I know people put a patina on carbon steel to help prevent rust, maybe doing the same thing with stainless will make it even more corrosion resistant?


but anyway for your purposes, the black oxide kit seems to be the ticket.

 

[driller86]

Now, Radio Shack sells an etchant for etching copper PC electronic boards. I've used it to make small IR flasher and variable DC power boards, but I can't think of it's name right now! It's a ferro-something or other. Well, anyway, it might work on stainless..... I should dig out my bottle and try it on a Mora.

Its called ferric chloride and it is what I use to etch damascus and it will also blackin carbon steel blades.

 

[handamerican]

I tried FC on stainless - didn't work for me. I thinks stainless is hard to affect.

When de rusting tool irons & such I've used electrolysis and Evaporust and both leave a battleship gray color on the metal.

If for nothing else then removing rust using electrolysis is cheap & easy:
http://www.youtube.com/watch?v=R5I5WBG5HPw

For creating a patina on high carbon steel take a look at the last video on the bottom of the page here:

http://www.chefknivestogo.com/vitu.html

This works pretty well.

You may have to copy/paste the URL's into your browser.

Keith

 

[pwet]

i've darkened a zdp blade pretty well using a, i quote, "synergic mix of acids", used to descale professional restaurant dishwashers. it's a pretty strong stuff that stained my stainless sink pretty bad ... that's where the idea to use it on blades came from.

it etches slowly, i had to heat the liquid. and let it soak a couple hours to get a "aged look" . then i polished it a little with 000 steel wool and a mild polish. it was darker than that just out of the acid but the surface wasn't smooth to the touch.
here it is with a quick cell phone pic without light.

440C is more stainless than ZDP for sure. but i'm pretty sure that a longer soak will yiel similar results.

hope this helps