Tips for Welding Aluminum in the Shipbuilding Industry
Aluminum alloys are lightweight and corrosion-resistant in marine environments, making the superior material for use in the shipbuilding industry.
There are two aspects that make general aluminum welding different from welding steel in the shipbuilding industry, and both are related to the fact that much of the welding is performed outdoors:
Storage of aluminum plates and extrusions is critical to avoid oxidation
Extra care must be taken to avoid breezes in the welding area
Both aspects will be discussed in more detail on the next few pages.
Know Which Aluminum Alloy You Are Welding
It isn’t enough to know that you are welding aluminum. Welding professionals have to know which alloy is about to be welded, and they have to know the correct filler metal to use. The most common alloys used in shipbuilding are the Al-Mg 5XXX sheet alloys and the Al-Mg-Si 6XXX extrusion alloys, primarily because of their excellent resistance to corrosion.
Most aluminum alloys are easily arc weldable. Virtually all of the alloys in the 1XXX, 3XXX, 4XXX, 5XXX and 6XXX series can be arc welded using GTAW and GMAW. However, most of the alloys in the 2XXX and 7XXX series cannot be arc welded. The only arc weldable alloys in the 2XXX series are 2219 and 2519. Almost all of the other 2XXX alloys will crack severely when welded. Similarly, the only alloys in the 7XXX family that can be arc welded are 7003, 7004, 7005 and 7039.
Specifically, be particularly wary of 2024 and 7075. It is tempting to buy one of these alloys for repair welding because they are strong and commonly available, but they are crack-sensitive to arc welding.
Welding an “unweldable" alloy or using the wrong filler alloy can result in immediate cracking or a premature failure in service at a later time.
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