I ruined the threading in my crank arm, and would like to weld or braze it back on, instead of buying a new crank set. It is a cheap old bike, so the result does not have to be perfect, but it should be cheap and durable.
I have welded on iron (an exhaust pipe and the like) in the past, and if this was just iron, I could fix it with no problems, but in this case it is not that easy.
Pedal arm: I think it is of aluminium. It seems light. Not magnetic. Looks like aluminium. I have no other guesses.
Pedal shaft: Steel, maybe even cast iron? I don't know how to tell the difference. It is definitely not aluminium. The material is stronger than the alu in the pedal arm, since the thread is intact. It looks sort of dirtyish / dark gray. Dark gray like some heavy parts in an engine which I believe are made from cast iron. Only slight rust despite a long life. Very far from the look of a stainless bolt.
Can you help me figure out what metals they are made from, so I can move on to finding the appropriate welding or brazing? Thanks.