Prop fouling is one of the biggest pains about having a boat in warm
waters. Even coating it with anti-fouling every year doesnt help as
the anti-fouling is blasted off by cavitation and sand. Using the
boat every week seems to help but if you use it less, soon you are
just giving the barnacles a thrill ride.
You might think that bronze props wouldnt foul due to their copper
content but the use of a shaft zinc suppresses Cu ions from going into
the water because the Zn is more electronegative. I have observed
that the shaft zinc doesnt seem to foul although it does sacrificially
erode. So, if Zn suppresses fouling, why not coat props with a thick
coating of Zn? This would not only protect the prop and related gear
from corrosion but suppress fouling.
I can imagine doing this either by electro-deposition or hot-dip
galvanizing. Hot-dip methods sometimes leave metal drips and other
flaws that would unbalance the prop but perhaps a better quality
process is available. The problem with Zn electro-deposition is that
the coatings are normally fairly thin. For work, I do Nickel and
copper electro-deposition to thickness up to 1 mm (.040") on a routine
basis. It is slow, taking over 48 hours but perhaps the same could be
done for Zn to produce a coating say .005" thick.
If such a service existed where you could send your prop every year or
two for such a caoting to protect it, how many people would use it?