Our Trillium brand vinyl liner pools have a non-corrosive structural polymer, (aerospace plastic) support wall. A structural polymer wall system has molded in horizontal, vertical and diagonal ribbing providing a much stronger and non-corrosive system than non-ribbed galvanized steel walls (sheet metal) that will eventually rust and corrode away in their moist environment. These wall panels are warranted by the manufacturer for as long as you own the pool!