Is this Patina or rust?

[JimboLawDawg]

I don't have any experience with 52100 steel. I forced a patina with 2-15 min white vinegar baths and then used some mustard for about 10 min.It doesn't look like the patina on any of my other carbon steel knives... The raised "crusty" portions kind of worry me a bit. Also, the color looks a bit off... Should I never dull it off and start over?Any suggestions are appreciated.

 

[Obsessed with Edges]

I see some of both patina AND rust.

Anything red or brown = rust. View it under BRIGHT LIGHT to see it more clearly for color. And especially if it's 'raised & crusty' as you describe. Rust causes the metal to expand to a volume greater than the space the metal originally occupied and it leaves deep pitting underneath it. After any forced patina using vinegar or other acids, scrubbing the blade with baking soda helps to neutralize the acid left and will also scrub away most of the red / brown rust, leaving some grey patina behind. Keep scrubbing the blade until the baking soda residue isn't showing any discoloration (red / brown) anymore. The red / brown rust is weakly bonded to the steel, so it flakes off more easily with scrubbing. Any of it that isn't removed can be scrubbed with some fine steel wool (#0000) to dislodge it.

The grey / black areas are dark iron oxide - usually called 'patina'. No harm there. The dark oxide 'patina' is more durable and won't be scrubbed away as easily, except with something like metal polish made for steel (Flitz, Simichrome, etc.) or other abrasive means like sanding, etc.

 

[JimboLawDawg]

I see some of both patina AND rust.

Anything red or brown = rust. View it under BRIGHT LIGHT to see it more clearly for color. And especially if it's 'raised & crusty' as you describe. Rust causes the metal to expand to a volume greater than the space the metal originally occupied and it leaves deep pitting underneath it. After any forced patina using vinegar or other acids, scrubbing the blade with baking soda helps to neutralize the acid left and will also scrub away most of the red / brown rust, leaving some grey patina behind. Keep scrubbing the blade until the baking soda residue isn't showing any discoloration (red / brown) anymore. The red / brown rust is weakly bonded to the steel, so it flakes off more easily with scrubbing. Any of it that isn't removed can be scrubbed with some fine steel wool (#0000) to dislodge it.

The grey / black areas are dark iron oxide - usually called 'patina'. No harm there. The dark oxide 'patina' is more durable and won't be scrubbed away as easily, except with something like metal polish made for steel (Flitz, Simichrome, etc.) or other abrasive means like sanding, etc.

Awesome, thank you for the tips!!! This knife is one of my Grail knives and I want to make sure it's cares for properly.

 

[eveled]

I use a spent brass rifle cartridge I flattened into a scraper. It will knock the rust or crust off, but not scratch the surface.

 

[MikeInTX]

Looks like a bit of both to me.

 

[scdub]

I use a spent brass rifle cartridge I flattened into a scraper. It will knock the rust or crust off, but not scratch the surface.

Gonna use that trick for sure!
Thanks!

 

[eveled]

Gonna use that trick for sure!
Thanks!

No problem. It even works on blued firearms. The trick is to do it dry. You want the abrasive rust dust to fall away.

 

[Crag the Brewer]

When I over do a forced patina that I'm not fond of I use Barkeeper's Friend.
It's a mildly abrasive powder for cleaning kitchen items.
I scrub it off.


Don't worry, 52100 is Awesome.
It gets blotchy, dark.....and Better.

Use it, Love it