Looks rusty enough. What software and tool did you use?

Photoshop

I don't see the rust, it just looks slightly tarnished. Use variations of red and brown if you want real rust.

Looks like you've laid down the foundation of the robotic head quite well but I personally don't like working with colours and adding depth immediately - unless you have everything planned out. It just saves time and effort if you have sudden change of ideas.

Cool head, you should throw some screws in it also agree with iawesome

Im just too afraid to add rusty effect on dirst wip lets see on next wip :3

Finally wip 2 :3

Haha, this is cool. The rust on the flat looks like nothing more than the spraypaint tool in MS Paint (my opinion), but it blends well on the actual head, I like it. My favorite touch are the three little wires coming out of the misplaced eye. I really want this one. Continue to work on it. It's cute.

Great work. It's like a metal baymax..
With the bottom jaw thingy, add a kind of scratch effect.

Sick a f!
Add more shadows to the wires. They look way too Bright.
I love the style and the rust.
Keep going.