First and foremost, steel WILL rust regardless of the pretreatment and top coat finish that is applied. Moisture is steel’s nemesis and considering the furniture is used outdoors, eliminating the moisture component is virtually impossible even if the furniture is placed in a covered or screened area. Steel is primarily used in “wrought iron” styles of furniture. Steel can be bent to create beautiful forms and details. Some of the techniques used in creating wrought iron furniture are centuries old. Generally, steel furniture is heavy and is a logical choice for windy outdoor environments. Wrought iron furniture is a popular choice and many consider this to be the first category of traditional outdoor furniture.
Aluminum furniture is created from either extrusions or solid cast aluminum. Many designs today, however, incorporate both extrusions and solid aluminum castings. An extrusion is best described as a hollow tube of aluminum usually formed with inner walls for added strength. The extrusions are made in a manner similar to how pasta is created. Solid aluminum cores or “billets” are pushed through a die shaped in the cross section profile of the desired look. The pieces are cut and bent into whatever shape the furniture requires.Aluminum can also be melted, poured into carved molds, cooled and welded onto extrusions to provide details that simple extrusions cannot provide. These aluminum parts are called cast aluminum components. Some outdoor furniture designs do not include the aluminum extrusions at all and are created entirely from solid cast aluminum parts. But, combining aluminum extrusions and cast components offer both weight and cost advantages. A solid cast aluminum chair can be extremely heavy and since aluminum is basically sold by weight, the resulting furniture would also be very costly. A benefit of combining extrusions with castings is in the additional weight. This weight, although modest, would prove beneficial in windy areas where slightly heavier outdoor furniture is required.
However, the biggest advantage when comparing aluminum to steel furniture- aluminum furniture will not rust. It is the perfect material to use outdoors and when coated with a baked on powder coated paint finish, outdoor aluminum furniture will last forever.
Original article: http://outdoorfurniturenews.com/aluminum-verse-steel/