Photos Remove stain on VG-MAX Shun Classic

[fedcas]

Hi,
I'm relatively new in the world of knives, slowly exploring the different styles and building up my set of knives... I recently found a good deal on a Shun Classic 6" Chef knife so i got it. It's my first VG-10 knife (actually VG-MAX, but I know there should be just minimal differences on the alloy composition and on the better side) and I understood it was much harder than German stainless steel but still quite effective in being stainless and not prone to corrosion. So I basically started using as I usually do with my other knives: processing food and leaving the knife aside on the cutting board as I cook and only after I have finished cooking (it could be after 30 mins or so), when i know I'm not going to use the knife again, I'll wash it (90% of times simply with water), dry it with a towel and put it back on the rack (or in its box, such as with this Shun).

For this Shun Classic Damascus I was a little bit worried that the damascus cladding might be delicate in respect of staining/corrosion (the darker bands should be some sort of carbon steel if I understood correctly), but I was surprised to see this stains apperaing instead along the VG-MAX core after just a few uses (I suspect tomatoes being the culprits):

(images are not the best, I'm sorry)

Basically there is this darker stain on the mirror finish core which I can't remove with soap and rubbing with a soft sponge/fingertip/nail. You can see also a little dark spot on the tiny primary bevel which I suspect being corrosion, as i can slightly feel it moving my nail on the edge. I've tried watching closely with a magnifying glasses and on that area the edge actually appears darker and matte and sligtly curving inwards (but not chipped, more on the smooth side).


On the other side instead. The two dark spots unfortunately are not stains but pitting corrosion or something similar: if I rub them with the point of a needle I can feel it catching on them slightly.

What do you think? In particular:

1) Best way I could try removing the stain and the oxidations? Maybe some leather stropping+polish to mantain the mirror finish? And some light sharpening on the waterstone for the edge corrosion?
2) What I have done wrong and how do I prevent it for the future? I particularly care about this knife both because it's my most expensive one so far and also because I may sell it sooner or later and get a good nakiri instead, since I use it way more.

Thanks in advance!

 

[KenHash]

) I would start with a polish, like Simichrome or Flitz. That should get rid of the stains, allowing you to work on the actual corosion.
To be honest while I've encountered rust on carbon steel knives, I have never seem rust on
any of my VG10 knives.
2) I do not think you are doing anything wrong. For what it;s worth, with my carbon steel knives I wash with soap/detergent as soon as reasonably possible using hot water (to expedite the evaporation) and wipe fully dry. If I am finished with use for the day I put a little Tsubaki Abura (Camelia oil) on the edge/blade.
This is a food safe oil used by all professional Chef's in Japan.

I would suggest trying this routine for a while and see if you still get a stain/corosion problem.

One question I will ask is if if you purchased this knife from a known seller/dealer and it is authentic.

 

[Saxman25]

I'm not sure how well this would work on SS stains, but flitz metal polish works wonders on any kind of staining like this on carbon steels. You would have to be a little careful with how you apply it because it may change how the cladding looks if it gets on it. For built up rust, fine brass wool can often gently scrub it off without affecting the finish on the blade. That's one of the reasons I would stay away from compound stropping, that method will abrade the face of the blade to remove the stain and will change how the finish looks.

I don't have much experience with vg-10 or vg-max, but I think these are plenty corrosion resistant enough to cut tomatoes and other acidic foods. I think the issue here might be letting the blade sit for too long wet with acid or salts on it, which is typically how SS corrodes. If you do end up getting a nakiri at some point, get one made in magnacut and you'll never have this issue, there's a lot of steels better than vg-10/max out there imo

 

[Spideyjg]

Second Flitz but use right on the stain. Use everywhere it will lighten the lines. Sadly the "pepper pitting" as I call it I see it commonly on Shun blades. Yours is minor but have seen pits going all the way through.

While on paper VG10 should be fine. My eyes see how they hold up to use. As Sax said in the last paragraph never let any blade sit with acidic food on it

 

[Lorien]

I say don't worry about it, and watch your knife gain some personality. Patina is character.

 

[Daniel L]

Put a dab of Flitz / Autosol / Brasso (basically any paste metal polish) on a paper towel and gently rub, it should come off easily. It looks like superficial surface patina... so if it bothers you, polish it out, but it should not affect knife function if you leave it.

If you don't like spots on your shiny knives, make sure you never buy a carbon steel kitchen knife!!

 

[Saxman25]

Pitting can unfortunately be pretty damaging and is normally associated with stainless grades in saltwater environments. It's a good idea to learn about it so you can prevent it from occurring again or worsening in the future. Here's an interesting article on pitting:

Pitting corrosion - facts and how to reduce the risk — Sandvik Materials Technology

www.materials.sandvik

A key takeaway if you ever get another knife is the fact that molybdenum and nitrogen contribute far more to pitting resistance than chromium, so looking for a molybdenum and nitrogen alloyed SS would be a good idea potentially. That might not hold up as well in higher carbon knife steels though because those numbers are for lower carbon constriction grade steels I believe.

 

[fedcas]

Sorry for replying after a few weeks, I finally gave the metal polish a try and it worked great! Thanks for all your tips. The stains were mostly superficial patina as you said and went away with a few good rubs. On the corrosion spots i also used some very fine abrasive paste rubbing gently with some paper, the two light pitting spots on the back of the blade are somehow still there (I can barely feel them with the tip of a needle, but much less than originally) but I cannot see them by eye so that's fine.

Basically all is left is this corrosion spot right on the edge:

(Yes, this time I used a macro lens )

By the way, i took many more pictures of the corrosion spot and of the damascus cladding pattern like this one:

Should you want to have a look here is the whole set:

https://imgur.com/a/fL3lSp5

P.S.
I really like the look of this knife, but I'm barely using it... so I decided to sell it now that it is in good condition. I will probably open another thread for advice on a good nakiri

 

[fedcas]

That was for the stain removal, now a separate update talking about the corrosion resistance... I was really surprised to see that also some brown rust developed on the back of the handle! the knife is of course not one piece, but the "cap" on the handle should be the same stainless steel as the node on the blade I guess?

You can see pictures here (it's 3 pictures):

https://imgur.com/a/bC9Q7lV

Luckily the rust was only superficial and I managed to clean it with the abrasive paste and a brush without affecting the brushed finish of the rest of the handle cap.