CATHODIC PROTECTION HANDBOOK & PRODUCT … · cathodic protection handbook & product guide. do not...

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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

[email protected]

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


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


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


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


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


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)


(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


Up to 28m2 Stud Fixed 4 x ZD78B 2 x ZD58

(300ft2) Welded (4 x ZD78) (2 x ZD77)


(300ft2) Welded (8 x ZD78) (2 x ZD77)


(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


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)


(600 - 900ft2) Welded (6 x AD78) (2 x AD76)

For Two Years in Salt or Brackish Water

fit the following Aluminium Anodes


Up to 28m2 Stud Fixed 4 x AD78B 2 x AD58

(300ft2) Welded (4 x AD78) (2 x AD77)


(300ft2) Welded (4 x AD78) (2 x AD77)


(600 - 900ft2) Welded (4 x AD73) (2 x AD77)

For Two Years in Fresh Water

fit the following Magnesium Anodes


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


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


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


ZD77M

2-95 core bar, 240 bolt centres


ZD78

Weld On Zinc Anode

4.5 Kgs Nom Weight

ZD78BM

Bolt-On Zinc Anode

5 Kgs Nom Weight


ZD77-CP

Chandlery Pack

Anode, Studs, Backing Sheet,

and Bonding Cable

CM200Z European


7 mm dia

0.2 kgs Nom Weight

ZD78B-CP

Chandlery Pack

Anode, Studs, Backing Sheet,

and Bonding Cable

CM500Z European


7 mm dia

0.5 kgs Nom Weight

CM1000Z European


7 mm dia

1 kg Nom Weight

ZD77Euro

Bolt-On Zinc Anode

2.4 Kgs Nom Weight


M10

ZD78B*

Bolt-On Zinc Anode

4 Kgs Nom Weight


ZD79

Bolt-On Zinc Anode

3 Kgs Nom Weight


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


ZD42/15"-2H Drilled


ZD42/18"-2H Drilled


ZD42/24"-2H Drilled

ZD42/24"-3H Drilled


ZD42/36"-2H Drilled

ZD42/36"-3H Drilled


ZD42/54"-3H Drilled



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)



P500/11⁄2"1/2" dia x 11/2" (use with PP375B Plug)












P1050/2"1.05" dia x 2" (use with PP1000B Plug)




PP250B Brass Plug for P375 Anodes -

1/4" NPT Thread

PP375B for P500 Anodes - 3/8" 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


ZSA98 shaft dia 25mm 0.50 Kgs

ZSA100 shaft dia 1" 0.45 Kgs

ZSA112 shaft dia 1 1/8" 0.41 Kgs










ZSA50 shaft dia 50mm








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








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


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


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


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


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



3.5 Kgs Nom Weight


0.4 Kgs Nom Weight


MD77 Bolt - On Magnesium Anode

0.7 Kgs Nom Weight


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)


1.1 Kgs Nom Weight

MD78B Bolt - On Magnesium Anode

1.0 Kgs Nom Weight


MD79 Bolt - On Magnesium Anode

0.8 Kgs Nom Weight



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



B56 Backing Sheet for ZD56


B72/B72BMLP Backing Sheet for ZD72/ZD72BMLP

B72B Backing Sheet for ZD72B

B76Euro Backing Sheet for ZD76 Mini Euro


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


Replacement Anode


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

For more product

information and

your local stockist

check out MGDuff on-line

CATHODIC PROTECTION HANDBOOK & PRODUCT … · cathodic protection handbook & product guide. do not...

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