Tubular hollow aluminum is used frequently for outdoor furniture. The tubes are cut and bent to create frame elements and then they are welded or bolted together. Tubular aluminum is lighter in weight so it may not be suitable for areas with high winds. It's durable and rustproof but not as sturdy as solid aluminum, so it is typically less expensive.
Wrought Aluminum is forged to create designs that are simple and elegant. Furniture that is made from solid metal rather than hollow tubing will be more substantial. Joints should be fully welded rather than bolted together for optimal durability. If joints are bolted, the hardware should be stainless steel or aluminum to prevent rusting.
Cast Aluminum is distinctly different from wrought aluminum furniture because of the incredible detail of its designs. Molten aluminum is poured into hand carved molds and allowed to cool to create striking designs. Cast aluminum is equally as strong, durable and weather-resistant, however the elaborate detail can make it more costly. All quality aluminum pieces will have a powder-coat finish that will give the metal its color and also increase its weather-resistance.