Aluminum doors (injected with urethane, 1 ¾­” thick doors) offer the advantage of being lighter (compare to a steel door) and therefore tend to be easier on their opening mechanism. In the long run, great savings can be made on maintenance costs since the mechanism will last longer. Other advantage: high resistance to salt air. However, when it comes to doors measuring 3,6 m (12 ft.) wide or less, there is little difference between aluminum and steel. Finally, remember that aluminum is recyclable.