just went thru this on an edger that was 20 - 25 years old. The replacement tank was about $25. Hardly worth messing fixing the old one. Where there is one crack there will be more coming if you don't have them already.
seems like every time I fix something like that with JB weld it fails somewhere else and then I kick myself because the part goes NLA in the meantime. I figure the original tank lasted 20 years, I am 68 and will be lucky if I last as long as the replacement.