chuck wrote:
Hello Frank,

Interesting comments.

My experience has been that it is not necessarily good or common
practice to bond all bronze through-hulls. It is rarely done in Europe,
and the ABYC makes clear that electrically isolated through-hull
fittings need not be bonded. While it is true that stray currents inside
the hull may cause corrosion of through-hulls, bonding through-hulls ".
. . causes corrosion due to stray currents outside the hull".
(Boatowner's Illustrated Handbook of Wiring by Charlie Wing)

To be honest I have no strong opinion either way, but I thought the
ABYC standard was unequivocal. In my 1998 copy they say:

"H-27.7.5.2 Metallic thru-hull fittings and drain plugs, installed
below the normal accumulation of bilge water, shall be bonded to the
boat's common ground point to minimize stray current corrosion."

Has their thinking changed since then?

Hello Jeff,

Thanks for the comment.

I don't have my copy handy, but I believe the section you quoted is a
special case: fittings installed below the normal accumulation of bilge
water. Fortunately, that is not the usual location for thru-hulls.
ABYC's reasoning is probably that should a hot wire come in contact with
the bilge water near the thru-hull, a corrosion circuit could be formed.
Of course, the wire itself would probably quickly corrode to nothing and
the problem would be self-correcting. More or less. At least there is an
identifiable benefit to bonding in this case.

Regards,

Chuck







Jeff wrote:
chuck wrote:

Hello Frank,

Interesting comments.

My experience has been that it is not necessarily good or common
practice to bond all bronze through-hulls. It is rarely done in
Europe, and the ABYC makes clear that electrically isolated
through-hull fittings need not be bonded. While it is true that stray
currents inside the hull may cause corrosion of through-hulls, bonding
through-hulls ". . . causes corrosion due to stray currents outside
the hull". (Boatowner's Illustrated Handbook of Wiring by Charlie Wing)


To be honest I have no strong opinion either way, but I thought the ABYC
standard was unequivocal. In my 1998 copy they say:

"H-27.7.5.2 Metallic thru-hull fittings and drain plugs, installed
below the normal accumulation of bilge water, shall be bonded to the
boat's common ground point to minimize stray current corrosion."

Has their thinking changed since then?