That looks like the rear bumper... correct?
If so, it is plastic... plastic does not rust.
If it is on another panel that is a metal substrate and the scratch has exposed bare metal, then yes, it will rust.
Megan EZ Coilovers|Trunk Lip|Roof Spoiler|Redouts|M2 Axle Back Exhaust|CF Vinyl Interior|GFX Sides
Xenon Depot 6000k HIDs & LEDs|MRR GF07 19x8.5+35/19x10.5+40|Hankook V12 235/35 & 275/30
I <3 Detailing