The alloy you choose for your aluminum sheet naturally depends on your application. 5005 Aluminum sheet is often used when the material will be anodized and deployed in an architectural application like flashings, sills, curtain walls etc. Architects often specify 5005 alloy for anodized aluminum architectural metalwork.
The importance of using an anodizing quality (AQ) alloy when the aluminum will be anodized cannot be overstated. Anodizing is an electrochemical process that converts the metal surface into a decorative, durable, corrosion-resistant, anodic oxide finish. When anodizing, the metal you start with has a tremendous impact on the quality of the finished product that you will receive. Simply stated 5005 AQ alloy is formulated for a decorative architectural anodized finish. It allows for a more uniform and attractive anodized finish than other alloys.
Finishing 3003 Aluminum
A good example of why one should never anodize 3003 aluminum.
DO NOT attempt to anodize aluminum alloys like 3003 or 3105 if you want the finish to be attractive and consistent. These alloys will show imperfections such as structural streaks, cloudiness, blemishes, and EXTREME color variation.
Many people substitute 5052 for 5005. While 5052 can produce acceptable results, it has more imperfections and is more prone to color variation than 5005 alloy aluminum.