Aluminum alloy type 2xxx is not a good corrosion resistance like other aluminum alloys. And under certain corrosion conditions, corrosion can occur along the grain edge. Aluminum grades of 2xxx are useful for high strength applications at temperatures up to 150 ° C (300 ° F) but except for grades 2219. This grade of aluminum alloy has limited weldability. But some types of alloys in this category have excellent processing. The 2021 grade aluminum is the most popular grade in aircraft production.