By all means, avoid welding 7075 series aluminum. You need to remember that some aluminum alloys are just not arc-weldable. This is one of those alloys. Another common aluminum alloy that falls into this category is 2024. Neither of these alloys was designed to be arc-weldable. In general, alloys in the 2XXX and 7XXX series are not arc-weldable, although they can be joined using other, specialized welding processes. Exceptions to this rule are alloys 2014, 2219, 2519, 7003, 7005, 7027, and 7039. Most of the other alloys in these families are unweldable. By “unweldable” I don’t mean you can’t fuse them together; in fact, you can, and the weld will look perfectly acceptable. The problem is that, because of the chemistry of these welds, they are prone to form microcracks in the weld and heat-affected zone. So while the weld appears visually acceptable, it likely will fail in service. The real difficulty is that both 7075 and 2024 are strong and commonly available. You can consult a catalog from a service center and find one or both of these alloys. You may be tempted to use them because of their high yield and tensile strengths, but avoid the temptation if you plan to weld.