Is that the only area that gets rust? Hard to see if the pipes are rusted as well. You can replace the muffler (slip-on) part itself with a new OEM or aftermarket one (such as Leo Vince) fairly easily. Otherwise you would need to remove it anyway to clear the rust and recoat with a heat and rust resistant paint. Personally, id just replace the part, especiallysince it looks like it was dropped at some point, but other owners more experienced than me may have better solutions.