How to remove darkness from pitting?

[Ericfg]

In the example here, noted by the arrow, how do I lighten the dark area of the pitting down by the edge? Obviously I could sand the pitting away but I don't want to do that. Is there something that will lighten that darkness?
The same could be asked about the makers mark but I want to leave that as it is. TIA.

 

[Se1ryu]

In the example here, noted by the arrow, how do I lighten the dark area of the pitting down by the edge? Obviously I could sand the pitting away but I don't want to do that. Is there something that will lighten that darkness?
The same could be asked about the makers mark but I want to leave that as it is. TIA.View attachment 187039

Do you try metal polish? Or stropping with compound?

 

[Benuser]

As it is patina and no rust you better leave it as it is. Otherwise, as it is so close to the edge I would see if you can polish it away with a 3k stone or so. I wouldn't insist too much, though.

 

[Harrison Cutlery]

Polish and a little dremel buffing wheel

 

[Ericfg]

Do you try metal polish? Or stropping with compound?

Good thought! I'll try a little barkeepers friend and see what happens.

As it is patina and not rust you better leave it as it is. Otherwise, as it is so close to the edge I would see if you can polish it away with a 3k stone or so. I wouldn't insist too much, though.

It's a table knife; it needs no edge and I don't want to create an edge on it. In fact, I can see that it was made with no edge as these 6 table knives are in nearly the same condition that they left the factory about 120 years ago.
Interestingly, I have a set of 1950s table knives that did come, obviously, sharpened from the factory, but this is not the case here. I worked hard with the sub-1k sanding and while that smoothed the raised part of the pitting somewhat it didn't address the, what shall we call it; ferric patina(?), that darkens the low spots of the pitting that sanding can't touch.

Polish and a little dremel buffing wheel

Good thought. I'll try barkeepers friend on a cloth wheel and see what happens. I'm not convinced, however, that that will get below the raised part of the pits.

 

[cotedupy]

An abrasive like barkeepers friend will certainly help.

Though remember, as you said, it's the result of previous rust pitting. And because of that it runs deeper than the kind of general light oxidation you'd call patina. The more you abrade - the more you'll get rid of it, which is why sandpaper does work best.

If you do want to concentrate on that particular section then I would suggest mud from a synth on a bit of cloth, and rubbed on hard with your finger. You can also use a thick bicarb paste in the same way, made with either water or even better - lemon juice. Or indeed toothpaste on a toothbrush (the proper abrasive white kind, not weird gel toothpaste.)

The very best thing for this method would probably be diamond paste mixed with a little mineral oil. But I imagine people are more likely to have the other options!

 

[Ericfg]

Or indeed toothpaste

I had that thought last night laying in bed. Thanks for the evidently subconscious suggestion.

 

[esoo]

Good thought! I'll try a little barkeepers friend and see what happens.

It's a table knife; it needs no edge and I don't want to create an edge on it. In fact, I can see that it was made with no edge as these 6 table knives are in nearly the same condition that they left the factory about 120 years ago.
Interestingly, I have a set of 1950s table knives that did come, obviously, sharpened from the factory, but this is not the case here. I worked hard with the sub-1k sanding and while that smoothed the raised part of the pitting somewhat it didn't address the, what shall we call it; ferric patina(?), that darkens the low spots of the pitting that sanding can't touch.

Good thought. I'll try barkeepers friend on a cloth wheel and see what happens. I'm not convinced, however, that that will get below the raised part of the pits.

Be aware BKF is an acid and can/will patina the knife. Have some baking soda on hand to neutralize it.

 

[Ericfg]

OK, here's some test work. Four pics;
1st image- original state with the ^ pointing to the spot to be worked on.
2nd image- in progress, bar keepers friend (BKF from now on) and white vinegar mix. Rubbed with Q-tip for around 60 seconds.
3rd- wiped off with tissue. Looks like the outer areas have been lightened. Patina from vinegar/BKF evident.
4th- rubbed about 60 seconds with BKF and water, and then wiped clean.

 

[Ericfg]

I tried toothpaste on the spot under the blue tape. I moved the blue tape to cover the work I did in the post above. I used a cotton swab, the tip cut off said swab for more force, and a toothpick. Poor results.

 

[Michi]

Simichrome might be worth a try.

 

[inferno]

i remember reading somewhere that citric acid can produce a bright surface. i tried it on SS that had some dark spots and it didn't do much on that particular steel. if you try it you need to keep an eye on it i'd say.

 

[Logan09]

Citric acid will turn metal a dull gray. And depending on the concentration it can and will pit/dissolve metal if you don't keep an eye on it.

 

[ReiHamono]

Diamond powder

 

[Se1ryu]

From seeing the updated pictures it looks like the blade rust very bad and deep. You need to remove a lot of metal to get rid that kind of rust. Maybe you can try CCK or any sabitoru/ rust erase medium then fine, or sandpapers, or diamond paste like @EricEricEric said and finish it with metal polish (Flitz, koyo blue or anything you have available).

Add: if you want to use sandpaper or diamond paste, start with lower grit then move up.

 

[inferno]

also. if you manage to the remove the dark color, it will probably come back pretty soon.

 

[sansho]

You want a reducing agent and/or chelating agent. Probably both combined with a detergent.

I know evaporust is a (regenerating) chelating agent. Give that a whirl.