Anodes for tanks
The only way of preventing corrosion in ballast tanks, when coatings become damaged or ultimately break down, is to apply sacrificial anodes.
Sacrificial anodes for tanks
Anodes can be customised to any design or compostion to suit most application and requirements. See the full product range of sacrificial anodes.
Below illustrations show the most common anode models applied in vessel’s tanks.
Water ballast tanks
Design considerations for cathodic protection of ballast tanks would usually include tanks’ size, shape and areas to be protected, coating system and ballasting routines.
A viable practice is to evenly distribute anodes over all the uncoated tank structure, with some emphasis on horisontal surfaces.
You may also want to read
Aluminium anodes are generally preferred over zinc anodes, as a result of its technical and economical advantages. There are, however, concerns using aluminium alloyed anodes in certain tanks due to the risk of sparking if the anodes fall off.
In cases where residual ballast water is expected to be left in the bottom of the tank, a low location of the bottom anodes should be provided, for example pitguard anodes mounted on the webs of bottom longitudinals. Provisions should then be made for higher (more continuous) anode consumption than initially expected.
You may also want to read
Cargo tanks
In oil and chemical cargo tanks, where there is a risk of a saline water layer settling in the bottom section of the tank, local corrosion attacks may occur. These attachs can be particularly severe in the presence of more noble metals in the water phase, like heating coils and pump units. Such units will make structural steel become anodic, and bare steel spots in the coating can experience rapid, galvanic corrosion. Read about forms for corrosion.
Pitguard anodes are easily clamped to bottom longitudinals to provide protection against corrosion during cargo voyages, when residual water settles in the tank bottom.
High temperature conditions
Conventional anodes tend to collaps at high temperatures. Therefore, the special HT-Anode, designed for elevated temperature conditions, should be used in tanks intended for the carriage of liquid cargo at elevated temperatures.
The HT-Anode is composed with the objective of obtaining consistent behaviour at ambient temperatures up to 90 °C.
