Am assuming these are mostly for AL, although their marketing materials show them "welding" copper pipe as well. Technically these are brazing rods for mostly AL I believe. Some people have had good results, the key being good surface prep (as usual). If you are trying to apply to a corroded surface you cannot clean they will not work for sure. My understanding is that like all brazing, they rely on the microscopic porosity of the base material. When these things were first introduced years ago everyone made fun of them as a gimmick. But they do have their place I think. For mostly esthetic repair and for lower strength cracks, they might be an OK solution. As a point of comparison, some people in reviews claim that FlexSeal works better...so take that as you may.
Most reviews say they are very messy, and score them both high and low. They seem to be targeted towards materials 1060, 1350, 3003, 3004, 3005, 5005, 5050, 6053, 6061, 6951, 7005 and cast alloys 710.0 and 711.0; they can be used on galvanized steel as well as copper. Supposedly.
There is a video on YouTube of these exact rods being used on a corroded AL boat bottom that cannot be prep'd properly. It doesn't go well. Personally, I think banjo music in the video's background dooms it to failure from the get-go—but then again I still can't watch Deliverance without doing a safety assessment of the other men in the room before the movie starts.
I have other low temp welding rods - for actual welding. There were rods made in like 80s and 70s for less powerful welders to weld. Seems they work ok and were gone once more powerful welders were available.
I got my Dad a buzzbox from auction for under 70 all in. Add to it 15 for a DC conversion bridge. Now he has a 230 amp max (probably more like 200 DC) welder for 85 CAD that is next to indestructible. Well, he actually as to finish installing the bridge so I am hoping it all will work well.
People did not have such cheap and easy power in 1980s and 1970s.
just throwing a bridge rectifier on an ac machine is only half the equation, you will probably still want to run ac welding rods due to the funky output waveform you will have as a result of not having any capacitors to smooth things out, i imagine without those arc stabilizers in an ac rod (potassium in the flux i believe) it may be hard to keep a nice steady arc going