Cathodic Anodes Australasia is the most trusted anode manufacturer in Australia. Their products protect boats, ships, yachts, and marine motors.

Aluminium Anodes

The sea water efficiency and driving potential of aluminium anode alloys is marginally better than zinc anodes. This means that in sea water, for an anode of equivalent dimensions, an aluminium anode will offer slightly better performance and slightly better performance and slightly longer life.
*Aluminium anodes may exhibit a lower rate of efficiency if used in brackish and freshwater when compared to zinc anodes. 

Alloys
Main Use
Seawater

Brackish Water
Freshwater
Soil
A1, A2, A6
Marine
Yes
Yes*
Yes*
No

Zinc Anodes

Zinc alloy anodes have been used for many years as a reliable means for providing cathodic protection. The universal benefits of being able of efficiently operate in sea water, brackish and fresh water is why zinc anodes continue to be very popular.
WARNING: At temperatures in excess of 50 degrees, hard non-saline waters (such as some fresh water cooling systems) may cause the polarity of a zinc anode/steel couple of reverse. That is, the steel may become anodic to the zinc anode and corrode at a rate more rapidly than existed prior to the installation of the anode. Seek the advice of a corrosion engineer if you expect to experience these conditions.

Alloys
Main Use
Seawater

Brackish Water
Freshwater
Soil
Z1
Marine and Soil
Yes
Yes
Yes
Yes Some low resistivity soils
Alloys
Main Use
Seawater

Brackish Water
Freshwater
Soil
Z2
Soil
No
No
No
Yes

Magnesium Anodes

Magnesium anodes have a high negative driving potential with makes them suitable for the protection of steel structures where the environment has a high resistivity, such as in soil and fresh water. Magnesium anodes are used extensively for the protection of buried piplines and also in hot and cold potable water applications.
WARNING: Magnesium alloy anodes should not be used in salt water without the advice of a corrosion engineer. The use of magnesium alloy anodes in sea water can cause major damage to coating systems on steel and aluminium hulls.

Alloys
Main Use
Seawater

Brackish Water
Freshwater
Soil
M1C
Freshwater Vessels, Soil & Hot Water Service (TDS: 0 – 40 mg/L)
No
No
No High resistivity water
Yes High resistivity soils
Alloys
Main Use
Seawater

Brackish Water
Freshwater
Soil
M2,M3
Freshwater Vessels, Soil & Hot Water Service (TDS: 0 – 600 mg/L)
No
No
No Medium/Low resistivity water
Yes Medium/Low resistivity soils