Viking VSC 61 FY User manual

Table of Contents
•Preliminaries
•Introduction
•Vessel Operations
•Fuel System
•Propulsion System
•Electrical System
•Electrical Safety
•Bilge Pumps
•Heating / Cooling System
•Fire Emergency
•Corrosion Protection
•Subsystems
•Water System
•Sanitation System
•Vessel Care
•Addenda
•Service Numbers Directory
VSC
61 FY
Owner’s Manual

Owner’s Manual
Corrosion Protection - 80 Viking Sport Cruiser 61FY
v1.0
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Corrosion Protection
This chapter describes the bonding system that protects
components against corrosion.
Major Topics:
The bonding system (overview) 81
Sacrificial zinc anodes 81
Running gear protection 82
Electrolytic corrosion 83
Stainless steel corrosion 83
Components attached to bonding system (drwg) 84
The Publisher’s Statements on
page i of this Owner’s Manual apply
to this chapter. Please read before
proceeding.
TABLE OF CONTENTS

81 - Corrosion Protection
Viking Sport Cruiser 61FY
Owner’s Manual
v1.0
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The Bonding System
Viking 61FY has a bonding system to protect the vessel
as much as possible from severe electrolytic corrosion of
propellers, shafts, rudders, fuel tanks, etc. caused by
electrical currents and warm seawater. Essential to the
cathodic protection system is an 8 gauge green and yellow
common bonding wire connecting protected components
to two sacrificial zinc anodes, port and starboard under
the hull.
Note:- The bonding wire must NEVER be connected to a
current carrying DC ground.
Metal graphite bonding brushes running on the prop shaft
inside the vessel protect the propellers and shafts by con-
necting them to the bonding system. The brushes must
always be in good firm contact with the shaft, and running
on a clean and shiny part of the prop shaft. If seawater salt
deposits are under the brush there is no protection.
At some marinas metal in the docks and stray electrical
currents in very warm seawater can cause severe corrosion
and vessels normally docked there need special attention.
Inspect zincs regularly and often (once a month may be
necessary in electrically active waters). Shaft zincs are
not recommended.
The vessel bonding system acts to reduce both galvanic
and electrolytic corrosion. These processes, especially in
warm seawater with elevated temperatures, quickly cause
extensive corrosion to any of a vessel’s unprotected metal
fittings exposed to seawater.
Sacrificial zinc anodes
Zinc anodes must be replaced once they are half their
original thickness. In Florida they have a short life, but it is
essential they be replaced, or there is no bonding and the
equipment they protect is at risk. Anodes are usually in-
spected and replaced by a diver unless the vessel is out
of the water. Visual inspection should show signs of corro-
sion or pitting –if anode corrosion is not apparent the
bonding system is likely not working and must be inspected
without delay. A simple continuity test inside the vessel
between the prop shaft and the two studs that hold the
zinc to the hull will confirm whether there is continuity.
Whenever the vessel is out of the water for service check
that anodes are not excessively corroded. If corroded, but
not down to half-thickness, they can be somewhat reju-
venated: remove the zincs, clean them with a wire brush,
clean off corrosion on the bolts, and reinstall. Never use
anti-seize lubricants, sealants or pipe dope to install zincs.
This would isolate them electrically from the metal they
protect and corrosion would result. There must be a good
electrical connection to the attaching bolts, which con-
nect to the bonding wire inside the vessel.
Continuous green
bonding wire
To clean the shaft and brushes . . .
Gently lift the spring loaded brush arms A. The prop
shaft MUST be clean and free of seawater deposits.
Zinc anode under hull.
There is one port; one stb.
Bonding
brushes
Bonding wire
Bolts must be
kept tight to
protect the
rudder
Tides shaft seal
Tides shaft seal
Rudder bonding
Zinc anode
A
keep
tight

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Running Gear Protection
Corrosion protection for the propellers, shafts and rud-
ders starts with selection of the best components and
materials to stand up to the severe warm salt water envi-
ronment typical of Florida, where unprotected metal is
quickly destroyed.
Prop shafts
Prop shafts are made by Teignbridge Propulsion Group in
Devon, England. They are 60 mm (2.3 in) Temet boat
shafting, precise to a tolerance of 0.003 inches out of
round to reduce vibration when rotating at high speed.
Galvanic corrosion is minimized by use of a specially for-
mulated metal that has a resistance to corrosion superior
to stainless steel –ie., it is below stainless in the active
and passive galvanic charts.
Propellers
Props are also by Teignbridge. They employ nickel-
aluminium and bronze AB2, for high running speed and
corrosion resistance. Props are 5-blade 30x42; shaft
threads are 42x3.Struts attach to the hull with large bolts,
with the nuts torqued down onto copper alloy backing
plates B (also called “P brackets”). Attached to these are
green bonding wires connected to the studs holding the
zinc anodes on the outside of the hull. This affords corrosion
protection to the running gear.
Zinc pencil rods
The MAN diesel engines and the Onan generator each have
internal zincs which MUST be replaced as scheduled –refer
to manufacturers’manuals for details. The ZF marine gear
also has zinc anodes on the oil coolers, near the seawater
inlet and outlet. Check annually or at 500 hours, or if
seawater leakage occurs.
Tides Marine self-aligning shaft seals
These comprise a simple nitrile lip seal on the shaft log
that blocks seawater to keep it from entering the vessel.
It is an important corrosion fighting strategy to prevent
seawater entering the engine room as much as possible.
Bow thruster protection
The Side Power bow thruster has its own protection against
electrolysis and corrosion. A zinc anode forms part of the
attachment nut for the propeller. Check this for erosion
whenever the vessel is out of the water, or have a diver
inspect it when installing main zinc anodes on the hull. Do
not ignore this anode, or corrosion will quickly attack the
thruster and its propeller.
Teignbridge prop and shaft
Bow thruster anode
Change internal zinc anodes on schedule
Bow thruster
zinc anode is
part of this nut.
B
P brackets, B
Struts connect to bonding
through these brackets
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Electrolytic corrosion
Stray currents are present at most marinas, and near other boats.
A particularly strong source is shore power cords lying in the wa-
ter –they cause severe corrosion, and are a safety hazard. At the
docks themselves there are often metal reinforcing rods in con-
crete that lie in the water. These conduct stray currents that can
cause a boat’s zincs to erode quickly. Stray current corrosion is
also caused by DC or AC current leaks from other boats around
you. Aluminum is particularly susceptible to this –just look at
some outdrives at a marina!
In the lazarette the two 15 kVA isolation transformers have a rated
input of 100 amps @ 240 volts. Shore power coming aboard is
isolated through the transformer windings from any direct contact
with outside grounds. ONLY red, black and green are brought into
the transformer. In effect, 240 volts AC ONLY goes into the pri-
mary winding of each transformer. 120 volt power is produced by
the transformer. This isolation protects against stray currents and
electrolytic corrosion that destroys underwater fittings.
In effect, the vessel has its own CLOSED CIRCUIT electrical sys-
tem which also protects crew and passengers from potentially
lethal electricity flowing through them to a shore ground.
The engines and generator have their own internal zinc anodes for
protection of their metal parts, these MUST be maintained ac-
cording to manufacturers’recommendations.
Stainless steel corrosion
All metals except gold, silver, titanium, and platinum corrode –
some much more than others. Despite its name, stainless steel
is also subject to corrosion because it is a ferrous alloy. 18/8
stainless, for example, is 67% iron, with 22% chromium and 11%
of other metals added to make it more resistant to corrosion. The
three types of stainless steels common in the marine industry
are 302 or 18-8, used for screws; 304, used for stamped parts;
and 316 or CF-8M, used for tubing, etc.
Though high up on the noble chart (-30 mV for resistance to cor-
rosion), stainless steel WILL rust quickly in its natural state, par-
ticularly in the warm moist climate of Florida. For stainless to be
corrosion RESISTANT it must be highly polished, plated, or electro-
polished in a number of ways during production. Unpolished stain-
less steel has iron or iron oxide sitting on the surface of the metal,
but polishing brings the chromium to the surface. The more shine,
the more resistance to corrosion.
If stainless is scratched, or cut and not polished at the edges,
corrosion will result. Thus, if a screw driver bit slips on top of a
screw, it will rust. And a hole drilled in stainless steel will corrode
inside the hole unless protected by a watertight sealer.
When washing the vessel, never let water dry on the stainless. To
avoid unsightly water spotting dry off stainless with a chamois.
Stanchions and rails must be kept clean, use a wax such as
Collinites 850 cleaner/wax to further protect them.
A corrosion and safety hazard
A shore power cord in the water is a hazard to
anyone in the water. The flow of AC current
inside the cable will also make the vessel more
susceptible to corrosion.
Isolation transformers
Isolation transformers effectively give the vessel
a ‘closed circuit”electrical system that is safe,
and will not leak current and cause corrosion.
Onan generator
Internal zinc anodes must be changed on schedule.
(optional model shown)

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Components Attached
to the Bonding System