Done a full test render so I can see how its coming along. Its only low quaility (720p, Max 16 samples and 0.5 Noise threshold) so theres quite a bit of noise that should disappear when rendered properly.
I've still got lots to do to it yet:
Add roughness map to each layer
Add another displacement mask around the paint bubbling to fade it in a little bit.
Change the strength of the Rust staining so its stronger on lower layers as they get revealed.
Add slow build up of surface grunge that flakes off as each layer falls away and starts rebuilding up on the next layer.
Create a invisible layer, so the material complete rusts out leaving holes in the robot.
I'm happy with how its coming along at the moment though, the entire process is procedural including the animation that run off of a single keyframe driver