The aluminum repair rod is a zinc/aluminum alloy. It is generally stronger than the base aluminum, but has little to low ductility compared to aluminum. So, the use depends on the application. I used some to repair a turn signal bracket which was part of a Krauser mount and it worked fine.
Having the aluminum really clean and using a stainless steel brush (used only on aluminum) to clean the hot aluminum surface and brush the surface when hot enough to melt the repair rod is needed. So much that brushing the aluminum while applying the rod to the hot aluminum is key. The technique is essentially soldering or brazing except no flux is used. The 'flux' comes from applying the stainless steel brush to remove the oxide layer when applying the rod.
The problems are the brittle repair and potential corrosion. For many applications, the lack of ductility is not an issue and paint will prevent corrosion. But, the aluminum for repair has to be hotter than the melting temperature of the rod.