There really is no reason to fake US Cents Environmental Damage, exposure to the elements can change the color of copper and copper coated zinc cents
Starting in 1983, US Cents are made of copper plated zinc instead of pure copper. A small amount of zinc gets into the plating bath, leading to yellowish coins. The more zinc the yellower, and at some point the plating bath is dumped and refreshed. It's considered a normal variation.