Applying a Rust Effect

Start by opening an image of metal wheels.

Select the black area by clicking magic wand on it.

Press Ctrl+shift+I to inverse the selection. Press Ctrl+J to copy & paste selection in a new layer. From filter menu select noise>>add noise. Apply settings as shown.

Press Ctrl+U to open hue/saturation window. Apply settings as shown.

Change the layer mode to hard light.

Ctrl+Click the layer thumbnail to get the selection.

From select menu apply modify>>contract.

Press Ctrl+J to copy paste the selection in a new layer.

Press Ctrl+U to open hue/saturation window. Apply settings as shown.

Change the layer mode to color dodge.