On 13/09/2019 13:15, AJH wrote:
I need to solder a patch onto a rusty diesel tank, previously I used
60/40 tin lead solder but this is not readily available locally will a
lead free plumber's solder still wet fluxed steel?


I don't know the answer to your question but, if you have a Toolstation
nearby, their product 81552 might (expensively) meet your 60/40 spec.

HTH

Nick