Creating a dirty, rusty interface requires great attention to detail. It is important that your textures don't look bland or flat. The following technique shows how quickly a nice pattern of damages appearing on the texture can be created.
Create a new layer and place your texture into it.
Apply Bevel and Emboss layer effect (Layer > Effects > Bevel and Emboss) to the layer with the texture. Set settings as shown on the image.
Add Mask² to the layer with the texture by clicking on the Add Layer Mask button in the bottom of the Layers palette.
Select the Airbrush¹ tool. Set black as the foreground color and select one of the nature brushes which comes with Photoshop 5.5. Paint softly on the texture layer's mask. This will create a very nice bevel effect.
;){kind=link}
With a little practice you will be able to create very realistic damages. You could also try using other textures instead of painting damages yourself.