Not a big deal on painted aluminum. If on bare aluminum it would be more an issue, but even then it will show you by not sticking well.

 

Not all silicone is acetic acid cure. Once cured, it's no longer corrosive. If it's okay, then leave it. If you can pull it off, it's not adhered well and may have some corrosion. You see the same thing on aluminum frame shower stalls where they used acetic acid cure silicone.

 

Thanks, stuck fine, it was on painted aluminum and I see no corrosion issues . It has a bed rug on the floor, and is sealed up with a hard tonneau, and better tailgate seal, gets no water or dust inside.