What is the grey stuff that comes on steel?

[blandies]

I was told when making knives to soak your piece of steel in vinegar before taking it to your grinder because the "scale" that comes on the steel will eat up your belts.

I had soaked a piece of steel in vinegar for 6 hours to remove this scale but when I removed it everything looked the same as when I put it in. So a few questions came up,,

Here is how the steel looks and on the far right you can barely see a shined silver area which is the bare steel,well what is everything else covering the bare steel up? It feels kind of rough and is gunmetal grey,,I thought this was the "scale"? If it is the vinegar did not remove it.

Then I seen this, if you look closely you can see cracks all along the edge..its like this all across the edges...is THIS the scale? The vinegar also did not remove that. Is this cracking normal.

So what am I supposed to be removing that will eat up my belts? That grey coating on the steel really feels to me like that would eat the belts right up but like mentioned the vinegar didnt phase it. I know the saying use belts like they are free but anything I can do to preserve them I will.

 

[Bill DeShivs]

That is just the steel surface, not scale.
The marks on the edges are where the steel was sheared off (cut.)

 

[Justin King]

That looks like the scale was sandblasted off before you bought it. This is becoming common, especially with cpm steels. About the cracking on the edge, I will have to defer to Mr. DeShivs.

 

[wolffbite]

Sorry for not getting back to your message sooner bud.

Yep, that doesn't look like scale. Scale would be more dark grey and uneven/flakey.

Just grind off the edges of the steel before you profile, those cracks don't penetrate into the stock any further than what you can see.

 

[Raymond1000]

I believe the gray stuff is patina. That's a low level oxidation that does not harm the steel. Many people force a patina on their blades because it's thought to protect against red rust. And because it looks cool. Soaking in vinegar is one way to force a patina.

 

[blandies]

Thats what I needed to know. I appreciate the responses and Wolffbite no problem ..Im just anxious to get started on this knife LOL. Which I am happy to say I am doing in a couple of hours. Need to get a checklist made before I start so I dont miss any steps.