...trust the name
MGDUFF INTERNATIONAL LIMITED
1 TIMBERLAINE ESTATE, GRAVEL LANE, QUARRY LANE
CHICHESTER, WEST SUSSEX PO19 8PP, UK
TELEPHONE: +44 (0)1243 533336
FAX: +44 (0)1243 533422
www.mgduff.co.uk
Yacht &
Powerboat
Issue 5.0
CATHODIC
PROTECTION
HANDBOOK &
PRODUCT GUIDE
DO NOT PAINT THE WORKING SURFACE OF THE ANODE DO NOT PAINT THE WORKING SURFACE OF THE ANODE
CORROSION WILL OCCUR IN ALL TYPES OF WATER
WITH DRAMATIC EFFECT
Metals of differing electrochemical potential when in contact with one
another form Galvanic cells. The metal with a lower potential in the
galvanic cell will be anodic and will corrode. The same effect can occur in
areas of different electrochemical potential in a single piece of metal such
as a steel plate. Any craft moored and operating in fresh, salt or estuarine
water is at risk from corrosion and the effects can be costly.
Corrosion on Steel & Aluminium vessels can be identified as either areas
of localised pitting to the hull plate, rudders, bilge keels etc. or less
obviously in the form of general wastage of the hull plating often occurring
below the paint coating. Pitting can lead to the complete penetration of the
hull below the waterline. General wastage of the steel can be just as
critical, weakening the hull and necessitating expensive re-plating.
Corrosion on Aluminium vessels is also generally in the form of localised
pitting to the hull plate, rudders, bilge keels and particularly in way of weld
seams. Pitting can lead to the complete penetration of the hull below the
waterline necessitating expensive re-plating.
On Wood and GRP vessels the areas of concern are principally the stern
gear i.e. The propellers, shafts, shaft brackets, stern tubes and rudders
which are expensive to replace and vital to the vessel, the failure of a
propeller or rudder could have disastrous consequences. The effects of
corrosion can vary from pitting of propellers and shafts to the
decomposition of the alloy of propeller. The failure of something as small
and inexpensive as a split pin can result in the loss of the propeller.
Stray current leakage is quite often cited as the cause of corrosion on all
types of vessel however more often than not the problem can be traced
to a galvanic action. Stray current leakage is the action of electrical current
from an external power source such as a battery or shore power supply
which because of some electrical system fault on board the vessel passes
out through the hull or a fitting in the hull and flows through the water
causing “Electrolytic” corrosion. Stray current leakage is usually a result
of damage or wear to the wiring system or poor installation of wiring or
electrical equipment.
WHAT CAN BE DONE TO PREVENT CORROSION?
The selection of materials is of prime importance in the construction of
craft. Generally naval architects and boat builders ensure that they select
metals which are as far as possible compatible to each other and when this
is not possible metals must be isolated from one another. There will always
be occasions when fittings or steel-work require replacement or repair and
it is important that when this is done attention is paid to the same criteria.
In particular ensure that fastenings and split pins are compatible and of
the highest quality. The paint system on any boat is an important first
barrier against corrosion. Seek advice from the paint manufacturers for
their recommendations on the most appropriate coating system and follow
the application instructions completely. Ensure that a good anti-corrosive
primer is applied if anti fouling is to be used. When using a copper based
anti-fouling none of the paint must be applied directly to bare metal
surfaces.
Vegetable oil based paints, although far less widely available than in the
past, should not be used with cathodic protection systems as the paint
tends to saponify.
The correct installation of electrics on a boat will reduce the possibility
of stray current leakage and the following actions are recommended:
• Use only high grade insulated wiring of suitable capacity. Undersized
wires will cause resistance and consequent voltage drop.
• Clip or support all wires at suitable intervals to prevent fatigue and
eventual fracture.
• Use only corrosion resistant terminals and connectors and make sure
that all are clean and tight.
• Attach only the main battery leads to battery terminals.
• Fit an isolation switch in the battery circuit.
• Ensure that all battery circuits are correctly fused.
• Keep all wiring, connections and junction boxes above the bilge area
and other areas likely to become wet.
• Make sure that when fitting additional equipment the work is carried
out in accordance with the manufacturer's instructions. The polarity of
connections should be correct and each circuit must be correctly fused.
• Electrical and Electronic work is best carried out by a qualified marine
electrician.
• Ongoing maintenance on your boat is essential. Metal work, paint
coatings and electrical installations all require regular inspection.
In particular you should inspect the wind and water line area if owning
a steel vessel. This area is particularly vulnerable because it is often
prone to mechanical damage but derives no protection from an anode
system being above the water line.
WHAT IS CATHODIC PROTECTION?
Cathodic protection is an electrochemical
process which halts the natural reaction
(corrosion) of metals in a particular
environment by superimposing an
electrochemical cell more powerful than
the corrosion cell. Sacrificial Anodes are fitted or
bonded to the metal to be protected which in
turn as it has a greater electrical potential than
the anode material becomes cathodic and
causes the anode to waste instead of itself. In a
correctly installed MGDUFF Cathodic Protection
System the only corrosion occurs to the sacrificial anode which is
replaceable. The number and size of anodes is determined by the type of
material and the surface area being protected.
The term bonding refers to the connection of the anode to a remote metal
component such as the propeller shaft or rudder stock and it should be
remembered that the integrity of the bonding is critical to the effectiveness
of the cathodic protection system.
Several factors determine the type of cathodic protection system fitted.
Firstly the environment in which the vessel is operating, secondly the
size and type of construction and finally the length of time that the vessel
is likely to be afloat before the next maintenance slipping.
FIT THE CORRECT ANODE MATERIAL FOR THE WATERS YOUR
VESSEL IS OPERATING IN
As a general rule owners should fit the anodes suitable for the environment
they most regularly berth in and the following table provides a useful guide:
Salt Water Fit Zinc or Aluminium Anodes
In Brackish Water Fit Aluminium Anodes
In Fresh Water Fit Magnesium Anodes
Some vessels will from time to time move between salt and fresh water,
others are berthed within marinas and behind tidal barriers where the water
is enclosed and likely to be brackish or even virtually fresh. Owners must
be aware of the effects that this may have on their boats and fit the correct
cathodic protection system to avoid corrosion.
Not all anodes are suitable for every environment, for example the surface
of a zinc or aluminium anode will if left in fresh water for some time
become covered with an off white crust of oxide which effectively seals the
anode and stops it working even when returned to salt water. Zinc Anodes
suffer a similar problem even in brackish conditions whereas Aluminium will
continue to operate effectively in river estuaries and other areas of brackish
water indefinitely. The consequences of this passivation of the anode are
that the next most anodic item within the anode bonding system will start
to sacrifice itself which could of course be very serious.
It is therefore very important to check Zinc and Aluminium anodes after
any trips into fresh water and if necessary clean off or change the anodes.
Should a vessel move into fresh water for more than two weeks MGDUFF
recommend that an alternative anode system is used suitable for fresh
water situations.
Magnesium Anodes on the other hand have a much higher driving voltage
than zinc or aluminium making them highly suitable for use in Fresh Water,
they will however become very active in salt water where they will probably
only last a matter of months. Protected surfaces can build up a layer of off
white calcarious deposit which will be difficult to remove.
Magnesium anodes are not designed for prolonged use in sea water
and if you are taking your boat into a salt water location for more than
seven days (Fourteen days in any one year) you should consider changing
the anodes.
Magnesium Anodes should never be fitted to wooden hulled vessels
as they can damage the timber.
2 3
DO NOT PAINT THE WORKING SURFACE OF THE ANODE DO NOT PAINT THE WORKING SURFACE OF THE ANODE
C AT H O D I C P R O T E C T I O N O F W O O D E N
A N D G R P H U L L E D V E S S E L S
To determine the number and size of anodes required, match the type
of vessel and select the anode suitable for the size of propeller and
the type of water
■ TYPE A Vessels are single screwed with a very short length of
propeller shaft exposed to the water and fitted with GRP or wooden
rudders. One anode will be required to protect the propeller and shaft
■ TYPE B Vessels are single or twin screwed with a long length of
propeller shaft exposed to the water supported by a shaft bracket.
One anode will be required to protect each shaft assembly. Bronze or
stainless steel rudders or GRP rudders with bronze or stainless steel
stocks should also be bonded to the same anode, however mild steel
rudders will require separate anodes.
■ TYPE C Vessels are single screwed with a long length of propeller
shaft exposed to the water supported by a shaft bracket and GRP
rudders with bronze or stainless steel stocks. One anode will be
required to protect the propeller, shaft and rudders.
For Type A, B or C Vessels
the following anode selection table applies
FOR EACH PROPELLER ASSEMBLY FIT ONE
Propeller In Salt In Salt or In FreshDiameter Water Brackish Water Water
250mm ZD56 AD56 MD56Zinc Anode Aluminium Anode Magnesium Anode
500mm ZD77 AD77 MD77Zinc Anode Aluminium Anode Magnesium Anode
750mm ZD78B AD78B MD78BZinc Anode Aluminium Anode Magnesium Anode
All schemes must be inspected annually and the anodes renewed if more than 50% wasted
CATHODIC PROTECTION OF WOODEN HULLED VESSELS
Wooden hulled vessels operating in fresh water are subject to the
same corrosion problems as GRP craft. However the fitting of
magnesium anodes is NOT recommended as they will have a
damaging effect on the timbers around the fixings known as
electro-chemical decay.
MGDUFF advise that the appropriate action is to fit a magnesium
shaft collar on the exposed propeller shaft and if necessary to fit
anodes directly to mild steel rudders and keels.
MAGNESIUM ANODES SHOULD NEVER BE FITTED TO THE
TIMBERS OF A WOODEN HULLED VESSEL
4 5
Propeller In Salt In Salt or In FreshDiameter Water Brackish Water Water
250mm ZD56 AD56 MD56Zinc Anode Aluminium Anode Magnesium Anode
All schemes must be inspected annually
and the anodes renewed if more than 50% wasted
■ TYPE D Vessels are those fitted with saildrives, sterndrives or
outboard motors. Most are fitted with sacrificial anodes specifically
designed for them, and MGDuff replacements may be found on pages
22-29. We recommend regular visual inspection of outboards and
sterndrives when moored, at least every 2-3 months, as the wear rate
of the anodes can be affected by a variety of factors:
• The degree of tilt of the drive – anodes must be fully immersed.
• Substitution of aluminium propellers by stainless steel versions.
• Addition of stainless steel accessories such as propeller guards
• Loss of electrical continuity – many sterndrives have small
continuity wires fitted between the component parts which must be
replaced if broken, and stainless steel clips on rubber gaiters can
loosen through pitting corrosion.
Saildrive anodes too can be
affected by bronze propellers
and stainless steel rope cutters.
In these circumstances we
recommend that a
supplementary anode is fitted
to the hull and bonded to the
transom plate or drive flanges
as shown:
SELECT APPROPRIATE ANODE:
B O N D I N G T H E C AT H O D I C
P R O T E C T I O N S Y S T E M
DO NOT PAINT THE WORKING SURFACE OF THE ANODE DO NOT PAINT THE WORKING SURFACE OF THE ANODE
F I T T I N G A N D B O N D I N G
S A C R I F I C I A L A N O D E S
WHEN FITTING ANODES TO WOODEN
OR GRP HULLED VESSELS REMEMBER:
• The anode should be positioned on the outside of the hull below
the waterline.
• The anodes can “see” the parts to be protected.
• The fixing studs are located above the bilges.
• The anode location ensures the minimum run of bonding cable
to the parts to be protected.
• There must be reasonable internal access to the studs.
• The anode should not be positioned forward of or in line with
Echo Sounding Transducers or log Impellers.
• Whenever an anode is fitted to a GRP or wooden hull an anode
backing sheet must be used to control the wastage
of the anode and protect the hull. The anode backing sheet should
be replaced each time the anode is replaced.
• Always ensure that the anodes are fitted with MGDUFF Fan Disc
Washers under the securing nuts which will help to assure the
contact between anode and cathodic protection system. The fan
disc washers and nuts should be replaced each time the anode
is replaced.
• Protect the anode fixing studs on assembly with paint
or grease inside and outside the vessel.
• The correct bonding of the cathodic protection system is imperative.
• Use 4mm2 PVC Insulated Multi-Stranded Copper Cable or larger.
• Ensure that all connections are clean and tight.
• The best way to bond the anode to the shaft is by using a MGDUFF
Electro Eliminator as well as bonding the anode to the gear box or
Engine casing.
• Insulated Flexible Couplings should be bridged by using a short
length of bonding cable or a copper strap to carry through the
contact between anode shaft and propeller.
• Bronze and Stainless Steel Rudders, Rudder Hangings and
Shaft Brackets should also be bonded to the main anodes.
• Trim Tabs should be protected with separate anodes.
• Do not bond the same anode to ferrous and non-ferrous metals.
Steel Rudders must be protected with separate anodes.
Hull Anode Installation
• Stiffen the inside of the hull where the anode is to be fitted
if necessary.
• Drill holes to take the fixing studs at the appropriate centres.
• On wooden hulled vessels studs should be sleeved or painted to
insulate them from the surrounding timber. When sleeving the stud
either use a heat shrink tube or ensure that the inside of the sleeve
is packed with marine grade sealant.
• Before inserting and securing each stud assembly, apply a generous
amount of marine grade sealant to the shank and collar where the
stud touches the hull to ensure a good seal.
6 7
CATHODIC PROTECTION OF ALUMINIUM HULLED VESSELS
Aluminium is an excellent material for boat construction,
but needs special attention regarding cathodic protection
and paint application. For anode selection and placement
refer to the technical sheets on the MGDuff website.
WHEN USING A COPPER BASED ANTIFOULING ENSURE NO
PAINT IS APPLIED DIRECTLY TO BARE METAL SURFACES
DO NOT PAINT THE WORKING SURFACE OF THE ANODE DO NOT PAINT THE WORKING SURFACE OF THE ANODE
WHEN DETERMINING THE CATHODIC PROTECTION
REQUIREMENTS FOR A STEEL HULLED VESSEL THE FIRST
CRITERION IS THE SURFACE AREA OF STEEL HULL BELOW
THE WATER LINE - THE WETTED SURFACE AREA.
This is calculated by multiplying the water line length by the sum
of the beam and draft i.e. LWL x (Beam+Draft). This calculation
will apply to most motor cruisers and sailing boats.
Once the wetted surface area is calculated, it can be applied to
the selection tables below from which the number of anodes
required can be taken.
8 9
C AT H O D I C P R O T E C T I O N O F
S T E E L H U L L E D V E S S E L S
For One Year in Salt Water fit the following Zinc Anodes
Anodes Area Hull per Rudder
Up to 28m2 Stud Fixed 2 x ZD78B 2 x ZD56
(300ft2) Welded (2 x ZD78) (2 x ZD76)
28.1 - 56m2 Stud Fixed 4 x ZD78B 2 x ZD56
(300ft2) Welded (4 x ZD78) (2 x ZD76)
56.1 - 84m2 Stud Fixed 6 x ZD78B 2 x ZD56
(600 - 900ft2) Welded (6 x ZD78) (2 x ZD76)
84.1 - 102m2 Stud Fixed 4 x ZD72BM 2 x ZD58
(900 - 1100ft2) Welded (4 x ZD80) (2 x ZD77)
102 - 148m2 Stud Fixed 6 x ZD72BM 2 x ZD58
(1100 - 1600ft2) Welded (6 x ZD80) (2 x ZD77)
For Two Years in Salt Water fit the following Zinc Anodes
Anodes Area Hull per Rudder
Up to 28m2 Stud Fixed 4 x ZD78B 2 x ZD58
(300ft2) Welded (4 x ZD78) (2 x ZD77)
28.1 - 56m2 Stud Fixed 8 x ZD78B 2 x ZD58
(300ft2) Welded (8 x ZD78) (2 x ZD77)
56.1 - 84m2 Stud Fixed 4 x ZD72B 2 x ZD58
(600 - 900ft2) Welded (6 x ZD73) (2 x ZD77)
84.1 - 102m2 Stud Fixed 6 x ZD72B 2 x ZD78B
(900 - 1100ft2) Welded (6 x ZD73) (2 x ZD78)
102 - 148m2 Stud Fixed 8 x ZD72B 2 x ZD78B
(1100 - 1600ft2) Welded (8 x ZD73) (2 x ZD78)
For One Year in Salt or Brackish Water
fit the following Aluminium Anodes
Anodes Area Hull per Rudder
Up to 28m2 Stud Fixed 2 x AD78B 2 x AD56
(300ft2) Welded (2 x AD78) (2 x AD76)
28.1 - 56m2 Stud Fixed 4 x AD78B 2 x AD56
(300ft2) Welded (4 x AD78) (2 x AD76)
56.1 - 84m2 Stud Fixed 6 x AD78B 2 x AD56
(600 - 900ft2) Welded (6 x AD78) (2 x AD76)
For Two Years in Salt or Brackish Water
fit the following Aluminium Anodes
Anodes Area Hull per Rudder
Up to 28m2 Stud Fixed 4 x AD78B 2 x AD58
(300ft2) Welded (4 x AD78) (2 x AD77)
28.1 - 56m2 Stud Fixed 8 x AD78B 2 x AD58
(300ft2) Welded (4 x AD78) (2 x AD77)
56.1 - 84m2 Stud Fixed 4 x AD72B 2 x AD58
(600 - 900ft2) Welded (4 x AD73) (2 x AD77)
For Two Years in Fresh Water
fit the following Magnesium Anodes
Anodes Area Hull per Rudder
Up to 28m2 4 x MD78 2 x MD56
(300ft2)
28.1 - 56m2 4 x MD73 2 x MD56
(300ft2)
42.1 - 56m2 4 x MD72 2 x MD56
(450 - 600ft2)
56.1 - 70m2 6 x MD72 2 x MD77
(600 - 750ft2)
NOTE When fitting and replacing bolt-on anodes always
ensure that the serrated fan disc washers are replaced
Six anode fixing plan - narrow boat
Four anode fixing plan - narrow boat
Electro Eliminator No2
- shaft earthing assembly
for propeller shafts over
40mm Dia excluding
mounting bar
Part No EE2/208
Whether your boat is steel, wood or GRP an MGDUFF Electro Eliminator
offers the best solution for bonding to your stern gear and achieving
maximum protection.
Running directly onto the propeller shaft the electro eliminator places
the anode on constant low resistance contact with the propeller shaft.
The copper graphite brushes will give at least 2000 running hours under
normal conditions. The electro eliminators will also remove the irritating
interference to electronic equipment caused by the rotating shaft.
E L E C T R O E L I M I N ATO R S
S H A F T A N O D E S
DO NOT PAINT THE WORKING SURFACE OF THE ANODE10 11
MGDUFF offer the widest range of shaft anodes in terms of type and
size and material.
It should be understood that this format of Cathodic protection
although simple to fit affords a far lower degree of protection to the
systems listed elsewhere in this brochure. In order to afford maximum
protection the surface area of the anode must relate in ratio to that of
the surfaces it is endeavouring to protect. A standard often impossible
to achieve due to the products design. The fitting of more than one
shaft anode can sometimes overcome this problem.
Available in Zinc and Magnesium
With built in core bar which holds the
anode firmly to the shaft through the
duration of its life
Available in Zinc and Aluminium
ZSC Zinc Shaft Collars
MGD – Super Shaft Anode
ZSA – Standard Shaft Anode
Designed for installation where only
a limited length of shaft is visible.
Available in Zinc and Magnesium
Electro Eliminator No1
- shaft earthing
assembly for propeller
shafts up to 50mm Dia
C/W mounting bar
Part No EE1
ZINGARD is one component cold applied zinc coating which contains
a minimum of 96% pure zinc when dry, providing cost effective and
reliable long lasting corrosion protection to all ferrous metals. Its dry
layer contains a pure zinc content of more than 96%, as well as
synthetic resins which allow the electrochemical bonding of the zinc
to the metal. ZINGARD is non-toxic and free from xylene, toluene,
Methyl-Ethyl-Keton (M.E.K.) and methylene chloride.
CREATES AN ACTIVE ANODIC ZINC LAYER THAT PROVIDES
CATHODIC PROTECTION TO EXPOSED METAL BELOW THE
WATERLINE.
CREATES A PASSIVE ZINC COATING THAT RESISTS CORROSION
ABOVE AND BELOW THE WATERLINE.
Properties
ZINGARD is safe and easy to use. It hardens on metal surfaces
and its excellent flexibility and adhesion prevents peeling off, with
exceptional resistance to mechanical shocks, abrasion and erosion
ZINGARD allows subsequent touch-up as it thoroughly mixes with
any previously applied ZINGARD coat.
Preparation
ZINGARD will only adhere to either roughened metallic surfaces or to
weathered galvanizing. Blast cleaning to SA 2.5 is highly
recommended on metallic surfaces. ZINGARD can be applied on to
corroded surfaces after first brushing off loose rust with a soft wire brush.
Typical Applications
Re-coats existing galvanizing on boat trailers, anchors, chains,
keels and underwater fittings, certified for fresh water tanks
(use with potable water to BS6920 (2000). Will protect pontoons,
handrails and all other steelwork above and below the waterline.
For commercial applications please contact our office.
500ml spray can
Z I N C A L L O Y H U L L A N O D E S Z I N C A L L O Y H U L L A N O D E S
12 13
40ZHD
Bolt-On Zinc Anode
4.5 Kgs Nom Weight
110 mm bolt centres, M16
ZD51
Zinc Disc Anode
0.5 Kgs Nom Weight
70mm dia, M10
ZD52
Zinc Disc Anodes
(Pair) with bolt
50mm dia
ZD55
Zinc Disc Anode
7 Kgs Nom Weight
225mm dia, M10
ZD56*
Zinc Disc Anode
1 Kgs Nom Weight
100mm dia, M10
ZD57
Zinc Hanging Anode
2.2 Kgs Nom Weight
3.0m cable and gib eye
ZD58*
Zinc Disc Anode
2.2 Kgs Nom Weight
150mm dia, M10
ZD59
Zinc Disc Anodes
(Pair) with bolt
70mm dia
ZD60
Weld On Zinc Anode
6 Kgs Nom Weight
ZD72B*
Bolt-On Zinc Anode
12 Kgs Nom Weight
229 mm bolt centres, M16
ZD72BM*
Bolt-On Zinc Anode
6.5 Kgs Nom Weight
200 - 229 mm bolt centres
M10 or M16
ZD72BMLP
Low Profile Bolt-On Zinc Anode
6.5 Kgs Nom Weight
200 - 229 mm bolt centres
M10 or M16
ZD75
Weld On Zinc Anode
0.5 Kgs Nom Weight
ZD73
Weld On Zinc Anode
10 Kgs Nom Weight
ZD76
Weld On Zinc Anode
1 Kgs Nom Weight
ZD76 Mini Euro
Bolt-On Zinc Anode
1.2 Kgs Nom Weight
Up to 110 mm bolt centres
M10
ZD77*
Bolt-On Zinc Anode
2.1 Kgs Nom Weight
200 mm bolt centres, M10
ZD77M
2-95 core bar, 240 bolt centres
240 mm bolt centres, M10
ZD78
Weld On Zinc Anode
4.5 Kgs Nom Weight
ZD78BM
Bolt-On Zinc Anode
5 Kgs Nom Weight
200 mm bolt centres, M10
ZD77-CP
Chandlery Pack
Anode, Studs, Backing Sheet,
and Bonding Cable
CM200Z European
100 - 135 mm bolt centres
7 mm dia
0.2 kgs Nom Weight
ZD78B-CP
Chandlery Pack
Anode, Studs, Backing Sheet,
and Bonding Cable
CM500Z European
113 - 150 mm bolt centres
7 mm dia
0.5 kgs Nom Weight
CM1000Z European
149 - 187 mm bolt centres
7 mm dia
1 kg Nom Weight
ZD77Euro
Bolt-On Zinc Anode
2.4 Kgs Nom Weight
100 - 210 mm bolt centres
M10
ZD78B*
Bolt-On Zinc Anode
4 Kgs Nom Weight
200 mm bolt centres, M10
ZD79
Bolt-On Zinc Anode
3 Kgs Nom Weight
200 mm bolt centres, M10
ZD80B
Bolt-on Zinc Anode Multifit,
8.5 Kgs Nom Weight
125 - 160mm bolt centres
M12 or M20
ZD80
Weld On Zinc Anode
8.5 Kgs Nom Weight
NOTE * OLD STYLE ANODES AVAILABLE AS SPECIAL ORDER ONLY
Z I N C S T R I P A N O D E S
ZD42/5"-2H Drilled
ZD42/6"-1H Drilled
ZD42/6"-U/D Undrilled
ZD42/12"-2H Drilled
ZD42/12"-U/D Undrilled
ZD42/15"-2H Drilled
ZD42/15"-U/D Undrilled
ZD42/18"-2H Drilled
ZD42/18"-U/D Undrilled
ZD42/24"-2H Drilled
ZD42/24"-3H Drilled
ZD42/24"-U/D Undrilled
ZD42/36"-2H Drilled
ZD42/36"-3H Drilled
ZD42/36"-U/D Undrilled
ZD42/54"-3H Drilled
ZD42/54"-U/D Undrilled
ZD42/72"-U/D Undrilled
M A R T Y R Z I N C S H A F T A N O D E S
Z I N C R O D C A S T I N G S L O N G
DIA LENGTH WEIGHT
ZR15 15 mm 400 mm 0.45 Kgs
ZR20 20 mm 500 mm 1.20 Kgs
ZR25 25 mm 500 mm 1.90 Kgs
ZR30 30 mm 500 mm 2.70 Kgs
ZR40 40 mm 500 mm 4.70 Kgs
ZR50 50 mm 500 mm 7.20 Kgs
ZR60 60 mm 500 mm 9.70 Kgs
ZR70 70 mm 500 mm 13.50 Kgs
ZR80 80 mm 500 mm 17.80 Kgs
ZR100 100 mm 500 mm 28.30 Kgs
ZR150 150 mm 500 mm 61.00 Kgs
Z I N C S H A F T C O L L A R S
DIA METRIC STD WALL
ZSC20 20mm 25mm
ZSC22 22mm 25mm
ZSC25 25mm 32mm
ZSC28 28mm 32mm
ZSC30 30mm 32mm
ZSC35 35mm 32mm
ZSC40 40mm 32mm
ZSC45 45mm 35mm
ZSC50 50mm 35mm
DIA IMPERIAL STD WALL
ZSC22 7⁄8" 25mm
ZSC27 11⁄8" 32mm
ZSC32 11⁄4" 32mm
ZSC38 11⁄2" 32mm
ZSC44 13⁄4" 35mm
ZSC57 21⁄4" 35mm
DIA METRIC THIN WALL
ZSC20T 20mm 15mm
ZSC25T 25mm 15mm
ZSC30T 30mm 15mm
ZSC35T 35mm 18mm
ZSC40T 40mm 18mm
ZSC45T 45mm 18mm
ZSC50T 50mm 18mm
Z I N C S H A F T A N O D E S W I T H C L A M P I N S E R T
DIA METRIC
MGD25mm 25mm
MGD30mm 30mm
MGD40mm 40mm
MGD50mm 50mm
MGD60mm 60mm
MGD70mm 70mm
DIA IMPERIAL
MGD3/4" 3/4"
MGD7/8" 7/8"
MGD1" 1"
MGD1 1/8" 1 1/8"
MGD1 1/4" 1 1/4"
MGD1 3/8" 1 3/8"
MGD1 1/2" 1 1/2"
MGD1 3/4" 1 3/4"
MGD2" 2"
Z I N C P E N C I L A N O D E S A N D
B R A S S R E TA I N I N G P L U G S
P375/2"3/8" dia x 2" (use with PP250B Plug)
P375/3"3/8" dia x 3" (use with PP250B Plug)
P375/4"3/8" dia x 4" (use with PP250B Plug)
P500/11⁄2"1/2" dia x 11/2" (use with PP375B Plug)
P500/2"1/2" dia x 2" (use with PP375B Plug)
P500/4"1/2" dia x 4" (use with PP375B Plug)
P500/6"1/2" dia x 6" (use with PP375B Plug)
P625/2"5/8" dia x 2" (use with PP500B Plug)
P625/3"5/8" dia x 3" (use with PP500B Plug)
P625/4"5/8" dia x 4" (use with PP500B Plug)
P625/6"5/8" dia x 6" (use with PP500B Plug)
P750/2"3/4" dia x 2" (use with PP750B Plug)
P750/3"3/4" dia x 3" (use with PP750B Plug)
P750/4"3/4" dia x 4" (use with PP750B Plug)
P750/6"3/4" dia x 6" (use with PP750B Plug)
P1050/2"1.05" dia x 2" (use with PP1000B Plug)
P1050/3"1.05" dia x 3" (use with PP1000B Plug)
P1050/4"1.05" dia x 4" (use with PP1000B Plug)
P1050/6"1.05" dia x 6" (use with PP1000B Plug)
PP250B Brass Plug for P375 Anodes -
1/4" NPT Thread
PP375B for P500 Anodes - 3/8" NPT Thread
PP500B for P625 Anodes - 1/2" NPT Thread
PP750B for P750 Anodes - 3/4" NPT Thread
PP1000B Brass Plug for P1050 Anodes -
1" NPT Thread14 15
G A LV I O N E L E M E N T S
G625 L 0.75" x .0.625" DiaG825 L 0.75" x .0.825" DiaG1050 L 0.75" x .1.050" DiaG1050M - -
no stud
ZSA75 shaft dia 3/4" 0.35 Kgs
ZSA88 shaft dia 7/8" 0.40 Kgs
ZSA98 shaft dia 25mm 0.50 Kgs
ZSA100 shaft dia 1" 0.45 Kgs
ZSA112 shaft dia 1 1/8" 0.41 Kgs
ZSA120 shaft dia 30mm 0.56 Kgs
ZSA125 shaft dia 1 1/4" 0.50 Kgs
ZSA350 shaft dia 35mm 0.68 Kgs
ZSA138 shaft dia 1 3/8" 0.68 Kgs
ZSA150 shaft dia 1 1/2" 0.61 Kgs
ZSA155 shaft dia 40mm 1.20 Kgs
ZSA175 shaft dia 1 3/4" 1.14 Kgs
ZSA178 shaft dia 45mm 1.10 Kgs
ZSA200 shaft dia 2" 0.90 Kgs
ZSA50 shaft dia 50mm
ZSA225 shaft dia 2 1/4" 2.66 Kgs
ZSA236 shaft dia 60mm 2.10 Kgs
ZSA250 shaft dia 2 1/2" 2.40 Kgs
ZSA270 shaft dia 2 3/4" 3.40 Kgs
ZSA300 shaft dia 3" 2.95 Kgs
ZSA312 shaft dia 31/2" 4.1 Kgs
ZSA401 shaft dia 4" 3.27 Kgs
AD79 Bolt - On Aluminium Anode
1.5 Kgs Nom Weight 200mm
bolt centres
M10
AD78B*Bolt-On Aluminium Anode
1.7Kgs Nom Weight
200mm bolt centres"M10
ASA20mm To suit shaft dia 20mm
ASA22mm To suit shaft dia 22mm
ASA25mm To suit shaft dia 25mm
ASA30mm To suit shaft dia 30mm
ASA35mm To suit shaft dia 35mm
ASA40mm To suit shaft dia 40mm
ASA45mm To suit shaft dia 45mm
ASA50mm To suit shaft dia 50mm
A L U M I N I U M S H A F T A N O D E S
W I T H C L A M P I N S E R T
A L U M I N I U M A L L O Y H U L L A N O D E S
F O R S A LT A N D E S T U A R I N E WAT E R S
16 17
A L U M I N I U M A L L O Y H U L L A N O D E S
F O R S A LT A N D E S T U A R I N E WAT E R S
AD56*Aluminium Disc Anode
0.4 Kgs Nom Weight
M10
AD57Aluminium Hanging Anode
0.8 Kgs Nom Weight
3.0m cable and gib eye
AD58*Aluminium Disc Anode
0.8 Kgs Nom Weight
M10
AD60 Weld On Aluminium Anode
2.5 Kgs Nom Weight
AD72B*Bolt - On Aluminium Anode
5 Kgs Nom Weight
229 mm bolt centres
M16
AD76 Weld On Aluminium Anode
0.5 Kgs Nom Weight
AD77*Bolt - On Aluminium Anode
1 Kgs Nom Weight 200mm
bolt centres
M10
AD55
Aluminium Disc Anode
2.8 Kgs Nom Weight
225mm dia
M10
AD78 Weld On Aluminium Anode
2 Kgs Nom Weight
NOTE * OLD STYLE ANODES AVAILABLE AS SPECIAL ORDER ONLY
M A G N E S I U M A L L O Y H U L L
A N O D E S F O R F R E S H WAT E R
18 19
M A G N E S I U M A L L O Y H U L L
A N O D E S F O R F R E S H WAT E R
MD56 Magnesium Disc Anode
0.3 Kgs Nom Weight
100 mm dia, M10
MD57 Magnesium Hanging Anode
0.8 Kgs Nom Weight with
3.0m cable and gib eye
MD59 Disc Anodes
(Pair) with bolt
70mm dia
MD72 Weld On Magnesium Anode
4.5 Kgs Nom Weight
MD72B Bolt - On Magnesium Anode
3.5 Kgs Nom Weight
229 mm bolt centres, M16
MD73 Weld On Magnesium Anode
3.5 Kgs Nom Weight
MD76 Weld On Magnesium Anode
0.4 Kgs Nom Weight
140 mm bolt centres, M10
MD77 Bolt - On Magnesium Anode
0.7 Kgs Nom Weight
200 mm bolt centres, M10
MD55
Magnesium Disc Anode
2 Kgs Nom Weight
225mm dia, M10
MSA 1 1/2"to suit shaft dia 1 1/2"
MSA 1 1/4"to suit shaft dia 1 1/4"
MSA 1"to suit shaft dia 1"
MSA 3/4"to suit shaft dia 3/4"
M A G N E S I U M A N O D E
MJE 1 For outboard and outdrive Leg
(See engine listings for
other magnesium anodes)
MD78 Weld On Magnesium Anode
1.1 Kgs Nom Weight
MD78B Bolt - On Magnesium Anode
1.0 Kgs Nom Weight
200 mm bolt centres, M10
MD79 Bolt - On Magnesium Anode
0.8 Kgs Nom Weight
200 mm bolt centres, M10
MD80 Weld On Magnesium Anode
2 Kgs Nom Weight
M A G N E S I U M S H A F T C O L L A R S A N D A N O D E S
M A R T Y R M A G N E S I U M S H A F T A N O D E S
MSA 98 to suit shaft dia 25mm
MSA 100 to suit shaft dia 1" (25.4mm)
MSA 125 to suit shaft dia 1 1/4" (31.7mm)
A N O D E F I X I N G S T U D S
E L E C T R O E L I M I N ATO R S
M10B Zinc Plated Stud Assemblies c/w Nuts
& Washers For Woodand GRP Vessels
M16B Zinc Plated Stud Assemblies c/w Nuts
& Washers For Wood and GRP Vessels
M10BSS Stainless Steel Stud Assemblies c/w Nuts
& Washers For Wood and GRP Vessels
M10B Stud Packs (5) Carded Packs of five
M10B Stud Assemblies
M16BSS Stainless Steel Stud Assemblies
c/w Nuts & Washers For Wood
and GRP Vessels
M16C Stud Assemblies c/w Nuts & Washers
For Steel Vessels
M10C Stud Assemblies c/w Nuts & Washers
For Steel Vessels
M10NW Nuts & Washers
A N O D E B A C K I N G S H E E T S
B42/6 Backing Sheet for ZD42/6"-1H
B42/12 Backing Sheet for ZD42/12"-2H
B42/15 Backing Sheet for ZD42/15"-2H
B56 Backing Sheet for ZD56
B58 Backing Sheet for ZD58
B72/B72BMLP Backing Sheet for ZD72/ZD72BMLP
B72B Backing Sheet for ZD72B
B76Euro Backing Sheet for ZD76 Mini Euro
B77 Backing Sheet for ZD77
B77Euro Backing Sheet for ZD77 Euro
B78B Backing Sheet for ZD78B
20 21
Electro Eliminator No2 - shaft earthing assembly for propeller
shafts over 40mm Dia excluding
mounting bar
Part No EE2/208
Electro Eliminator Adaptor - for Tides Marine Series One Shaft Seal
Part No EE1 S1
Electro Eliminator No1 - shaft earthing assembly for propeller
shafts up to 50mm Dia C/W
mounting bar
Part No EE1
22 23
M E R C U RY/ M E R C R U I S E R M E R C U RY/M E R C R U I S E R K I T S
■ CM31640Z ■ CM31640A ■ CM31640M Mercury/Mercruiser & Honda - Standard Skeg
■ CM55989Z ■ CM55989A ■ CM55989M Mercury/Mercruiser - Button
■ CM34127Z Mercury/Mercruiser - Long Skeg
■ CM34762Z Mercury/Mercruiser - Plate
■ CM43994Z - CM821631Z■ CM43994A - CM821631A■ CM43994M - CM821631MMercury/Mercruiser - Block
■ CM46399Z Mercury/Mercruiser - Cut Down Skeg
■ CM821630C2Z ■ CM821630C2A ■ CM821630C2M Mercury/Mercruiser - Bravo Plate
■ CM821629CZ ■ CM821629CA ■ CM821629M Mercury/Mercruiser - Alpha Plate Gen II
■ CM818298Z ■ CM818298A ■ CM818298MMercury/Mercruiser - Outboard bar
■ CM826134Z ■ CM826134A ■ CM826134MMercury/Mercruiser - Wedge - & Honda 75
■ CM806190Z ■ CM806190A ■ CM806190M Mercury/Mercruiser - Bravo Lift-RamHorseshoe
■ CM806189Z ■ CM806189A ■ CM806189M Mercury/Mercruiser - Alpha Lift-RamHorseshoe - Gen II
■ CM806105Z ■ CM806105A ■ CM806105M Mercury/Mercruiser - Bearing Carrier Anode - Alpha II
■ CM762145Z ■ CM762145A Mercury/Mercruiser - Circular Plate - New Generation (Threaded Hole)
■ CM762144Z ■ CM762144A ■ CM762144M (2004+) Bravo 3 Plate (Through Bolt)
■ CM76214Z ■ CM76214M Mercury/Mercruiser - Circular Plate
■ CM865182Z■ CM865182A ■ CM865182M (2004+) Bravo 3 Prop Shaft Anode
■ CM89949Z Mercury/Mercruiser - Bracket
■ CM43396Z Mercury/Mercruiser - Waffle Bar
■ CM822157Z Mercury/Mercruiser - Trim Tab -
Merc. 30-50 hp
■ CM98432-5Z Mercury/Mercruiser - Outboard Anodic
Plate Bar
■ CM806188Z ■ CM806188A■ CM806188MMercury/Mercruiser - Bearing Carrier
Anode - Bravo I
■ CMBRAVO23KITZ■ CMBRAVO23KITA■ CMBRAVO23KITMAnode Kit for Mercury Bravo 2 & 3
■ CMBRAVO1KITZ■ CMBRAVO1KITA■ CMBRAVO1KITMAnode Kit for Mercury Bravo 1
■ CMVERADO6KITAMercury Verado - 6cyl Kit
KEY ■ ZINC ■ ALUMINIUM ■ MAGNESIUM KEY ■ ZINC ■ ALUMINIUM ■ MAGNESIUM
All kits include fixing bolts and instructions.
V O LV O P E N TA
■ CM832598Z ■ CM832598M (873179)■ CM832598AVolvo Penta - Dogbone
■ CM838929Z Volvo Penta - Pencil Anode
■ CMV15 (875810)Volvo Penta - Small Ring(100 Drive)
■ CMV16 (875809)Volvo Penta - Small Ring(200 Drive)
■ CMV17 (875805)Volvo Penta - Medium Ring(270 Drive)
■ CMV18 (875815)■ CMV18M (876137)■ CMV18AVolvo Penta - Large Ring(280/290 Drive)
■ CM823661Z Volvo Penta - Pencil Anode
■ CM358407Z (3586963)■ CM358407M■ CM358407AVolvo Penta - Sail Drive Ring(130/150)
■ CM3858399Z Volvo Penta - Folding Prop Ring Anode
■ CM875821Z ■ CM875821M (876138)■ CM875821A
■ CM852835Z ■ CM852835M (873178)■ CM852835AVolvo Penta - Bar
■ CM851983Z ■ CM851983ZM (876604)■ CM851983ZAVolvo Penta - Sail Drive Ring (120)
■ CM875812Z (876286)■ CM875812M (876603)■ CM875812AVolvo Penta - Sail Drive Ring (110)
■ CM872793Z■ CM872793AVolvo Penta - Triangle for 290, 290DP, SX, DP-X
■ CM872139Z■ CM872139AVolvo Penta - Bar for DP-X drive
■ CM3855411Z■ CM3855411M■ CM3855411AVolvo Penta - Transom Plate for SX drive
■ CM3854130Z■ CM3854130M■ CM3854130AVolvo Penta - Gimbal Plate for SX drive
■ CM852018 Volvo Penta - Folding Prop 100S, 110S, 120S, S-B, S-C
■ CM3841427AVolvo Penta transom block for DPH drive
■ CM3883728AVolvo Penta Cavitation Plate for
DPH drive
24 25KEY ■ ZINC ■ ALUMINIUM ■ MAGNESIUM KEY ■ ZINC ■ ALUMINIUM ■ MAGNESIUM
Volvo cross refs in brackets.
M E R C U RY/M E R C R U I S E R K I T S
■ CMALPHAKITZ1■ CMALPHAKITA1■ CMALPHAKITM1Anode Kit for Alpha 1 Gen I
■ CMALPHAKITZ■ CMALPHAKITA■ CMALPHAKITMAnode Kit for Mercury Alpha 1 Gen II
■ CMBRAVO3KITZ■ CMBRAVO3KITA■ CMBRAVO3KITMBravo3 (2004+)
27
M A X-P R O P
■ CMMP63RZ MULTIFITMax-Prop - 63mm dia (38mm I.D.)
■ CMMP70RZ MULTIFIT Max-Prop - 70mm dia(42mm I.D.)
■ CMMP83RZ MULTIFIT Max-Prop - 83mm dia(46mm I.D.)
H O N D A
■ CM6644537101Z ■ CM6644537101M
Yamaha & Honda -
Cut Down Skeg
■ CM6E04525111Z
Yamaha & Honda - Small Block
■ CM826134Z ■ CM826134A
Mercury/Mercruiser - Wedge -
Honda 75
■ CM06411ZV5Z
Honda - Small Bar - 35-50hp
■ CM06411ZW1Z
Honda - Large Bar - 75-115hp
■ CM31640Z ■ CM31640A ■ CM31640M
Mercury/Mercruiser & Honda -
Standard Skeg
S U Z U K I TO H AT S U
CM5532095310Z
Suzuki - Small Block
CMS551259630Z
Suzuki - Cutdown Skeg
CMS5512587D00Z
Suzuki - Standard Skeg
CM3C7602181A0Z
Suzuki Tohatsu
Transom bar
KEY ■ ZINC ■ ALUMINIUM ■ MAGNESIUM
For Original and New stylePropellers
26KEY ■ ZINC ■ ALUMINIUM ■ MAGNESIUM
V O LV O K I T S
■ CMDPHKITAAnode Kit for Volvo DPH
All kits include fixing bolts.
■ CMV290KIT■ CMV290KITM■ CMV290KITAAnode Kit for Volvo 290
■ CMV280KIT■ CMV280KITM■ CMV280KITAAnode Kit for Volvo 280
■ CMSXKITZ■ CMSXKITA■ CMSXKITMAnode Kit for Volvo SX
CMV290DPKIT ■
CMV290DPKITM ■
CMV290DPKITA ■
Anode Kit for Volvo 290 DP
CMV280DPKIT ■
CMV280DPKITM ■
CMV280DPKITA ■
Anode Kit for Volvo 280 DP
28 29
B O M B A R D I E R J O H N S O N / E V I N R U D E
T R I M TA B
■ CM123009Z
■ CM123009M
Small Block
■ CM367Z
Waffle bar
■ CM982277Z
Waffle block
■ CM392462Z
Small Horseshoe
■ CM392123Z
Half Moon
■ CM393023Z
Block
■ CM983494Z
Horseshoe
■ CM433580Z
Anode for Power
Trim and Tilt Models
■ CM984513Z
■ CM984513M
Horseshoe
■ CM984547Z
Block
■ CM327606Z
Block
■ CM980756Z
Plate
■ CM398331Z
Block
■ CM431708Z
Curved Block
■ CM983952Z
Block
■ CM397768Z
Block
■ CM398873Z
Donut
■ CM389999Z
Wedge
■ CMBNT1AZ
Zinc anode for Bennett Trim
Tabs and similar
KEY ■ ZINC ■ ALUMINIUM ■ MAGNESIUM KEY ■ ZINC ■ ALUMINIUM ■ MAGNESIUM
YA N M A R
■ CM272100200300Z
Yanmar - Pencil Anode
■ CM19642002652Z■ CM19642002652M
Yanmar - Sail Drive Anode
YA M A H A
■ CM6644537101Z ■ CM6644537101M Yamaha & Honda - Cut Down Skeg
■ CM6G54525101Z Yamaha - Handlebar
■ CM6H14525102 Yamaha - Bar
■ CM6884537102Z ■ CM6884537102M Yamaha - Skeg
■ CM6E04525111Z Yamaha & Honda - Small Block
■ CM6E54525100Z Yamaha - Small Block
■ CM6K14537100Z Yamaha - Skeg
■ CM6E54537101Z Yamaha - Skeg
■ CM6J94537100Z ■ CM6J94537100M Yamaha - Skeg
■ CM6884525101Z Yamaha - Button
■ CM61N4525101Z Yamaha - TrimTab Anode
■ CM61A4537100 Yamaha - Skeg
■ CM69L4537100Z Yamaha - HPDI / V Max Skeg
30 31KEY ■ ZINC ■ ALUMINIUM ■ MAGNESIUM
B U K H
■ ZBU1
Bukh - Zinc Pencil
A R N E S O N
■ ARNSMALL
Arneson - Small teardrop
■ ARNLARGE
Arneson - Large teardrop
B E N E T E A U/J E A N N E A U
■ CMAN225 Beneteau Type - 22/25mm
Replacement Anode
■ CMAN230 Beneteau Type - 30mm
Replacement Anode
■ CMAN235 Beneteau Type - 35mm
Replacement Anode
■ CMAN240 Beneteau Type - 40mm
Replacement Anode
■ CMAN245
Beneteau Type - 45mm
Replacement Anode
ANODE LOG
Boat Name:
DescriptionPart DateNo. Changed
Hull Anodes
Rudder Anodes
Shaft Anode
Trim Tabs
Sterndrive Type
Saildrive Type
Engine Anodes
MG DUFF PRE-SEASON CHECK LIST
Check: ■for any sign of corrosion to stern gear
and other hull fittings ■that your anodes will last for the duration
of next season ■that the surface of the anodes are free
of paint and chalky corrosion deposits ■that anode bolts are secure, nuts
and washers clean and sound ■all internal bonding wires clipped securely,
insulation and connections sound ■Electro Eliminator springs for tension,
brushes clean and correctly positioned ■
you are fitting the correct anode: ■Salt Water: Zinc or Aluminium ■Brackish Water: Aluminium ■Fresh Water: Magnesium ■
when fitting a new anode replace
the serrated fan disc washer and nuts ■replace backing sheets on GRP and
wood hulls ■grease or paint exposed studs, nuts
and washers after assembly ■
✓
www.mgduff.co.uk
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information and
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check out MGDuff on-line