Overplating or re-plating an old tjalk, that may well be iron, is a pretty specialist business.
To consider:
A lot of overplating adds extra weight and some consider removing the old plate better so moisture is not trapped between the skins.
Tjalks have a soft-chine and flat bottom so getting the profile of the steel right is important. I saw them bend metre-long sections in a big press then offer them up to be welded.
In France where I saw it they charged by the metre but can't remember the price - not cheap.
I suggest you get specialist advice, perhaps start by joining the Dutch Barge Association