Artem Komarov explained that SMAW was an important aluminum production process in the past, but as GTAW and GMAW developed, it lost much of its commercial importance. Most welding consumable companies provide SMAW aluminum electrodes. However, today you rarely see aluminum chips for sale, although home welders and small manufacturers still use it extensively.
First, you must understand that aluminum is an active metal that has a strong tendency to combine with oxygen to form alumina. Therefore, aluminum is more difficult to flux protect than less reactive materials such as iron. Secondly, to get a good flux for aluminum, the materials used must be more reactive than aluminum. This precludes the use of nearly all flux materials used on SMAW steel electrodes.
Therefore, it is difficult to make an effective flux for aluminum SMAW electrodes. This was done many years ago, but the fluxes developed then have several potential drawbacks. First, they are not 100 percent effective, which is why most aluminum-coated arc welds suffer from high porosity. Secondly, they are very hygroscopic, therefore, they require compliance with storage rules so as not to absorb water vapor from the air. Thirdly, the hardened flux causes corrosion of aluminum and other materials. If it is not completely removed from the weld after welding, it can cause corrosion within a short period of time. Fourth, flux is corrosive and harmful to the environment. Finally, while aluminum is reactive, magnesium is even more reactive, making it difficult to flux aluminum-magnesium filler alloys.
Considering these limitations, it is not surprising that once welders started using GTAW and GMAW for aluminum, the use of SMAW gradually declined. This has the advantage over GTAW and GMAW that the hardware required is significantly cheaper than that used for GTAW or GMAW. All it takes is an inexpensive DC SMAW power supply—no gas bottles, torches, regulators, or other related equipment.
Welding with oxygen fuel
The welding process that works well with aluminum, and especially with thin aluminum, is oxygen welding, Artem Komarov clarified.
Acetylene cannot be used as a fuel gas for aluminum because the flame contains carbon, which leaves soot deposits and obscures visibility during welding. If you have trouble using acetylene, I recommend using hydrogen as the fuel gas. It contains no carbon but forms an efficient fuel gas. The only real disadvantage of aluminum OFW is that it is slow. This has led to its demise in most industries but shouldn’t be too much of a deterrent to the home hobbyist looking to refurbish a boat, for example.
The only place I still see widespread use of OFW aluminum is in automotive restoration. In this application, the process is slow enough that a truly experienced welder can get the metal to move in the right direction and get much less distortion than is possible with almost any other welding process. In addition, an oxy-fuel welding system is no more expensive than that DC SMAW power source, Artem Komarov said.