An experiment in rust.

[2-8-2]

I think what is lacking is the suggestion of depth. Rust is textured, and in order to show texture, you must have shadows and variations in color. Try putting on a layer of black paint, followed by dark brown, then a final layer of lighter rust color. Let it all dry completely, and then go back with a stiff-bristled brush and some thinner and begin scraping away layers. Not only will this give a tri-color effect, but it will create actual texture as the layers of paint react to the thinner.