Body questions : Longs, rust, etc., I found a hole... Options

[jsteele22]

So I've been working on my RH hell hole area as time, weather, and motivation allow. Using a wire wheel wasn't cutting it, so I got some blue (AlO2) gringing wheels for the electric drill. In the affected areas, I seem to cut through (in order) : colored paint, black layer, powdery rust, shiny metal.

Q1) The black layer is very tough, and doesn't seem to appear in areas where no rust occurred. Could this be some PO's rust converter job ? There is definitly some rust under the black stuff.

The rust situation is not bad in general. Apart from the battery tray, which I removed, there are no rusted through areas. But I've been a little worried about how strong the remaining metal is after pitting due to rust and then my grinding. Then, down in the very worst part of hell, not far from the "drain" hole, I found a tiny (1/16") spot that looked like a hole. I went at it pretty agressively with a blunt grinding wheel and found this :



My first thought was that the rust had started to penetrate outwards from a deep pit and form a large flake. So I went at it with a screwdriver, and started prying up the top layer. Here's what I found. (Although the rust-colored dust really stands out in the flash picture, in real life everything looks quite a bit cleaner.) :



And here's where it's located :


In the close-up, you can see smooth, grey primer surfaces between the two layers. In real life, the bottom layer looks clean and rust free (apart from the rust powder.)

Q2) What is going on here ? Are there really supposed to be two layers of metal ? How far does the 2-layer portion extend ? ( It doesn't look like a repair job to me, but ya never know...)

Q3) Although there aren't any more rusted-through holes, the metal in the deeply pitted zone is pretty flimsy, or at least it will be when I grind the rust off (like the part I pulled up with a screwdriver). What should I do : small patch just to seal the hole ? Cut out "top" layer of pitted metal and replace it ? Leave pitted layer in place and patch over it ? Bondo and sell to Ferg ?