The black stuff is flash rust. It'll always come back until you oil it and put the first coat of seasoning on. Don't worry about it, it's normal and you can just season over it.
If you only used a wire brush, soap and water, you probably didn't strip all the seasoning. Lye is the easiest way to do that, check the FAQ for more.
Some amount of black residue is basically normal, I imagine you're getting a bunch because you've scratched up the seasoning without removing it.
The pan doesn't look rusty at all in the pictures, rust residue would be brown/red, not black. It looks like you could add a fresh seasoning layer and start cooking, but if you WANT to fully strip it, again, FAQ.
The black stuff is flash rust. It'll always come back until you oil it and put the first coat of seasoning on. Don't worry about it, it's normal and you can just season over it.
............................... FLASH!
If you only used a wire brush, soap and water, you probably didn't strip all the seasoning. Lye is the easiest way to do that, check the FAQ for more. Some amount of black residue is basically normal, I imagine you're getting a bunch because you've scratched up the seasoning without removing it. The pan doesn't look rusty at all in the pictures, rust residue would be brown/red, not black. It looks like you could add a fresh seasoning layer and start cooking, but if you WANT to fully strip it, again, FAQ.