Turning a healthy metal photo into a rusty one can be useful for 3D designers.
This is a texture I made recently as part of a bigger texture package.
All of the work was done using the Gimp image tool. Gimp has a lot of the same features as Photoshop and it is free.. just a little gimpy.
I started with a photo of a barrel stove. The metal is solid and in good condition, perfect for rusting.
A lot of the images I make textures from are at slight angles so it was cropped using the Free Select tool with 4 points selected, the corners of the stove door.
After cropping, the image was made square using the Perspective tool. A little Brightness/Contrast adjustment commenced. As you can see, that mysterious fluid residue has been removed from the door surface.
To make it look rusty, I opened a hi-res image of a rusty metal surface. Using the Clone tool, I first selected a point on the rusty image and then went back to the door image and applied it to various areas at about 20 percent opacity using a textured brush, changing the brush size and shape a few times.
It is somewhat tricky to make it look legitimate but I'm convinced that this door is indeed rusted.
The texture images are free to use in your design projects if you please, no credit required.