In addition to our blog “The Vessel General Permit in a nutshell” there some additional requirements to comply with regulations on discharges that include those from anodes.
In general: what are anodes?
The anode or galvanic anode attached to your vessel is used to protect buried or submerged metal structures from galvanic corrosion. This form of corrosion occurs when two different metals in a conductive liquid (such as water) come close together. In simple terms, an electrical current is generated naturally between the two metals, rather like a battery, and the metal most likely to corrode will do so at a far faster rate than the metal that is less likely to corrodes.
Anodes aren’t just on the bow of a ship, but also on the seals. Attached to the liner, the anodes will make sure that the liner and housing parts don’t corrode.
Vessel General Permit
With regard to cathodic protection, the EPA VGP directives that cover non-military commercial vessels longer than 79 ft call for owners to select anodes “with metals that are less toxic to the extent technologically feasible and economically practicable and achievable.” The traditional zinc anodes contain percentages of highly toxic cadmium, a heavy metal whose use and disposal are becoming increasingly restricted and regulated.
Environmental friendly alternatives
According to the VGP, vessels have to change from zinc to aluminum or magnesium anodes where this is possible. The material to be used depends on where the vessel is used; for salt water the recommendation is aluminum and for fresh water, magnesium. If zinc is used after the first dry docking after 19 December 2013, then the reasons why aluminum was not selected need to be properly documented. If there are technical reasons why aluminum anodes could not be used, a statement to this effect can be obtained from the supplier.
Green solutions
Lagersmit is always keen to provide the best sealing solutions for vessels. These include environmentally-friendly anodes that will ensure you comply with the VGP directives, so we are able to supply aluminum anodes when requested.