I have the same grief in keeping antifoul on props - But is it OK to put
Zinc on top of Bronze? I have noticed that different metals together (say
aluminium rivets into stainless) seem to promote electrolytic (or some) type
corrosion.

regards Shawn
"Scallywag"
Brisbane Australia

"Parallax" wrote in message
om...
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?