[tt]I would be extremely wary of welding directly onto a conductor that is also acting as a pile.
The weld class from a fatigue standpoint is likely to be very poor and you run a risk of any crack which initiates in the weld migrating to the main body of the conductor pipe with catastrophic consequences.
It would probably be safer to have a riser guard clamped onto the conductor rather than welded. This will also be easier and quicker to install than a welded solution.[/tt]