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About corrosion
Corrosion takes place in all types of water and the impact on boats and coastal structures can be catastrophic. MGDUFF marine cathodic protection systems help prevent this kind of damage, protecting boats and structures and the investment in them.

All commercial and leisure vessels and onshore structures are vulnerable to corrosion. How does corrosion happen? In layman’s terms, a metal will corrode as a result of a chemical reaction to its surroundings, such as water.

Corrosion takes place in all types of water – fresh, salt and brackish – and as a result of an increase in the number of tidal barriers and enclosed marinas, boats of every kind are now regularly moving between all three. It is vital that the right anodes are used for each type of water.

This is why cathodic protection products from MGDUFF are so important. Our high-quality anodes, manufactured to strict quality and environmental standards, offer enhanced protection against catastrophic damage and costly repair bills.
What is cathodic protection?
Cathodic protection is an electrochemical process that halts the natural corrosion of metals in a particular environment, such as water.

In scientific terms, it works by superimposing an electrochemical cell more powerful than the corrosion cell. Put more simply, it diverts the corrosive process away from the metal components of a boat or structure and onto the anodes. These anodes are attached to the metal components of a boat or structure and, because they are made of a metal higher placed in the galvanic series, they attract corrosion and protect against damage. The anodes corrode instead of the boat or structure.

The number and size of anodes that should be used depends on what a boat or structure is made from and the size of the surface being protected. Also, the size of a boat or structure, the type of water it is used in and the length of time it spends in the water have a bearing on how often the anodes should be replaced.
Choosing the right anode
Generally speaking, the type of anode depends on the kind of water. The following is a useful guide:

Salt water -Zinc or aluminium anodes
Brackish water – Aluminium anodes
Fresh water – Magnesium anodes
Of course, boats often move between different waters, travelling between salt and fresh water, or being berthed in marinas or behind tidal barriers where the water is enclosed and brackish.

It is important to note that not all anodes are suitable for every type of water. For example, zinc and aluminium anodes are not suited to fresh water. If they are exposed to fresh water for a prolonged period, they become covered in a white oxide crust that effectively seals the anode and stops it from working when the boat returns to salt waters. Zinc anodes suffer a similar problem in brackish water.

Magnesium anodes are not suited to salt water. They become much more active than usual and this accelerated activity shortens the lifespan of the anodes and can leave a build-up of an off-white calcareous deposit that is difficult to remove. Also, magnesium anodes should never be fitted to wooden hulled boats as they can damage the timber due to a process known as electrical chemical decay.

MGDUFF recommends that boats that move into fresh water from salt water or vice versa for more than two weeks should have their anodes changed.

FIND YOUR ANODE

ZD76
Zinc Weld on Anode. For use in Salt Water only.
eight (kg): 1.0kg
Overall Length: 160mm
Anode Length: 114mm
Width: 76mm
Depth: 32mm

ZD77 MG DUFF ANODE

Zinc Bolt on Anode. For Salt water use only
Weight (kg): 2.1kg
Overall Length: 229mm
Anode Body Length: 153mm
Width: 83mm
Depth: 41mm
Stud Size: M10
# of Fixing Holes: 2
Fixing Hole Details: 19mm x 11mm fixing holes at 200mm hole centres

ZD78B

ZD78B
Weight (kg): 4.0kg
Overall Length: 305mm
Anode Body Length: 305mm
Width: 76mm
Depth: 32mm
Stud Size: M10
# of Fixing Holes: 2
Fixing Hole Details: 19mm x 11mm fixing holes at 200mm hole centres

ZD78
Zinc Weld on Anode. For use in Salt Water only.

Weight (kg): 4.5kg
Overall Length: 385mm
Anode Length: 305mm
Width: 76mm
Depth: 32mm