POR-15 has been used too. Long discussion on this several years ago.
I've never understood why Tormach ships the stands with the machine facing surfaces already painted. Seem like it'd make much more sense to just admit that the stand is going to leak (that seems to be the universal experience). Despite sealant in the seams. So, why not protect those surfaces temporarily (peel-off, washable anti-rust coat, something) and send along a can of sealant to make a full-coat overall seal? Make that part of the final assembly.