Battery Tray/Rust Spot after washing truck

The original battery in 2002 GMC Sierra failed(started leaking) and was replaced. Now with the third battery installed a problem has started after washing the truck. Within a few hours find a rust spot on the pavement beneath the battery area. No doubt the battery tray is the source of the rust. My question is how difficult is it to remove and replace the tray or is it welded in place? Another option besides replacing tray? Any input appreciated. TIA