How to remove black rust (?) caused by vinegar

[Bamba]

Hello folks!

So, I thought it would be a good idea to soak my alox lumberjack in vinegar (%5) for a few hours (because I was not happy with the w&t after the normal washing and oiling).
Ended up overnight in the acid...

What a mistake.

It developed this black patina you can see under the blade tip and on the combo tool (mostly on inner edge) and many other spots on the knife.
I immediately washed and soaked it in baking soda, then dried it and sprayed with WD40. I left the WD40 on for 3 days, and then tried to rub the black stains off with microfiber towel. It did nothing.

What exactly is this black thing? Any idea on how to remove it?

Bamba

[kamakiri]

I’d try almost any metal polish. 

[nate j]

It developed this black patina...

You've answered your own question.  It is starting to patina, forming a thin layer of iron oxide (rust), which can actually range in color from red to yellow to brown to black, depending on the conditions under which it develops.  Stainless steel "stains less", but is not immune to rust, especially when chemicals or salt water are involved.  The good news, as kamakiri notes, is that you should be able to polish it out with some metal polish.

[Bamba]

Thank you guys,

I'll try metal polish.

[pomsbz]

Flitz

[Bamba]

Flitz

Nice to get a reply from a local fellow 
Can you advise about buying Flitz in Israel, or a good alternative available locally.

Toda,
Bamba

[pomsbz]

Nice to get a reply from a local fellow 
Can you advise about buying Flitz in Israel, or a good alternative available locally.

Toda,
Bamba

You can get it easily from Amazon. They ship it out here. Or if you're in Jerusalem feel free to come round and use some, it only takes a tiny amount.

https://www.amazon.com/dp/B00FBPGVL6

[Sawl Goodman]

Those stains look like the battery acid stains I got on one of my knives a couple of weeks ago. I found Brasso useless. I’ve mostly removed it using sandpaper - 600 grit followed by 1000 grit. I’ll finish it with 2000 grit when I get some and live with a little lustre as the knife is a long time user anyway,

[Bamba]

You can get it easily from Amazon. They ship it out here. Or if you're in Jerusalem feel free to come round and use some, it only takes a tiny amount.

https://www.amazon.com/dp/B00FBPGVL6

Thanks, added to cart...

[Bamba]

Those stains look like the battery acid stains I got on one of my knives a couple of weeks ago. I found Brasso useless. I’ve mostly removed it using sandpaper - 600 grit followed by 1000 grit. I’ll finish it with 2000 grit when I get some and live with a little lustre as the knife is a long time user anyway,

 
Mine is also a user, my usual pocket edc actually. Would be crazy expensive to get a new one so I should be more careful with the one I have.
I guess if the Flitz doesn't work I'll hand it over to a pro knife shop.

[pomsbz]

Mine is also a user, my usual pocket edc actually. Would be crazy expensive to get a new one so I should be more careful with the one I have.
I guess if the Flitz doesn't work I'll hand it over to a pro knife shop.

The flitz should work fine, here it is removing vinegar stains from carbon steel, your Victorinox is stainless so it will come off a lot easier. I don't know of any 'pro' knife shops in the country to be honest, certainly none who would do any better than you can with your flitz.