I’ve owned a Dutch built Steel yacht for the last 10 years and it is now 32 years old.
Corten steel was used to build the Hull, House, cockpit
and all wet lockers.
Steel boats rust from the inside out, so the quality of its coating and welding on the inside will determine the lifespan regardless of the kind of steel used.
Since my boat has circumnavigated twice the hull has obviously worked over the years, but I have yet to find rust even where continuous welds were not possible and in those hidden away places that are all the usual suspects.
This year I removed all the original insulation
from the engine
room and I was especially concerned about the hull sides where 4 large Air Vents would have allowed salt water inside, in heavy going.
Did find it very salty and dirty, but the original green coating and inside shell was completely rust free.
A good cleaning
, light sand and prime of corners before 2 coats of white 2 part poly and I honestly believe it will be good for another 32 years.
In 2010, I sandblasted the hull down to white metal and found it to be completely blemish free, except for a small spot on the stern quarter (size of about 1 inch in diameter) where something had been happening.
inside revealed that under the aft storage
floor, a Zinc ingot had come loose and had scratched thru the interior
I am guessing it had created a hot spot in marinas
for galvanic action.
Ultrasound tested that the plating was to original spec and that blemish was simply filled with rod and the inside recoated.
So I don’t know how to convince anyone about the value of Corten steel, but I am very happy with it as I have worked on a lot of other mild steel yachts, that all needed some re-plating work after 20 years.