Not so much a failed weld as incomplete. You can see the rust trail lead right to the weld bead. My guess is the stress during use has caused the coating to crack and like the other comment mentioned it's now rusting from the inside. Obviously this is just my opinion but for now it looks serviceable. That said replace it as soon as you have the means, don't play around with your life or livelihood. You could also take it to a welder to grind out the area and reweld. After welding you can use a cold galvanizing paint to protect it but regularly monitor it for failure.