The first thing necessary for stick welding on aluminum is to have a machine capable of DC (direct current) polarity, and it must be capable of putting out at least 200 amps. If your welder meets these guidelines, you are in business. If you have a 120-volt, 140-amp machine, for instance, there is no way it will ever weld on aluminum. Voltage and amperage are the key.
Set the current on the machine. You will need a welder capable of at least 200 amps to successfully weld aluminum materials. Set the machine to between 190 and 210 amps, depending on the thickness of the material to weld. Unfortunately because of the deep penetration that stick welding aluminum creates, it is only recommended for quarter-inch and thicker material in most cases.
Watch the length of your arc. Generally, when stick welding aluminum, the arc length should be about the same as the diameter of the aluminum rod. Holding the rod too close to the aluminum decreases the voltage and compromises penetration. Holding the rod too far away increases the voltage but will cause porosity in the weld as well as lots of spatter. With a little practice, keeping the arc at a steady distance from the work becomes second nature.
Angle the rod at about 15 degrees against the aluminum being welded. If the rod is held straight up and down, it may not produce a clean arc, and the weld will be compromised. Holding it at 25 degrees or more will result in poor penetration and cause the weld to be weak. Drag the rod away from the weld rather than pushing into the weld as one might do with an MIG wire feed setup.
Develop a weld style and stick with it. Some people like to weld in a straight bee-line, which will produce a fine weld in most cases. Others like to make little "C" traveling arcs with the welding rod, which will create a weld that resembles a stack of dimes. Another technique is to zig-zag the rod back and forth across the gap, pausing for a second at each side before continuing diagonally over to the other side. All these styles work equally well, and it is purely a matter of taste which you choose for your own stick welding. Just remember to travel slowly to ensure a good puddle and nice penetration. Aluminum cools and dissipates heat very quickly, which is why it needs more amps. Therefore moving the rod as slowly as possible will keep the alloy heated well enough to weld.