Tecnoseal Answers - Anodes and Performance: a Wanted Balance
Today's Tecnoseal Answers is also dedicated to cathodic protection in the marine environment. The topic we will be discussing, was suggested to us by one of our website visitors who asked the following question (actually a very frequent one): "But sacrificial anodes affect the performance of a boat? And if so, how?"
Before we start, I remind you that at the following link you can find a thematic index of all the Tecnoseal Answers released until today.
a photo of the "projecting" submerged parts of a boat
The relationship between anodes and performance
We have already mentioned in numerous passed articles the relationship that inextricably links performances and sacrificial anodes, a type of connection that can be easily understood by anyone who knows the basics of the resistance to motion (otherwise you can always find them here, here and here). The shape of the hull of each boat is studied to have high dynamic performances and allow the vehicle to reach high speeds. The faster the hull, however, the more the presence of anodes on it will affect its dynamics. The presence of the anodes will indeed create turbulence that will affect the structural parts that generate and define the boat's motion . Furthermore, the opposite is also true, namely that the boat's dynamics and its speed also influence the consumption of the anodes itself. The same turbulence that impacts on the hull, can consume the anodes in an anomalous manner and alter the balance between them and the boat, eliminating the cathodic protection present as the calculation of the anodic plan will not correspond to reality.
Before continuing with the solutions to this problem, it should be noted that when we talk about how anodes affect the dynamics of a boat, in most cases we do not refer to the hull as a whole, but to those parts of it that are in contact with water (always or in any case for large amounts of time) and have a "protruding" shape. This is because, already basic, in the presence of these forms, certain types of turbulence will be created. We refer to parts of the boat such as: the shaft arms, the propeller area, the stern area, all the parts that are near structural fins, the keels and bulbs of sailboats, the foils of the high-speed boats and hydrofoils and anything else that is similar to what we have just listed.
a group of plates with a rounded profile
The Solution in Brief
Since a modern boat cannot sail without installing sacrificial anodes, since it would certainly be damaged by galvanic corrosion, there is no absolute solution to this problem and every shipowner/captain/worker knows that he must look for the best possible balance between installed anodes and actual performance. Fortunately, nowadays, there are many solutions that allow you to achieve excellent results without putting your boat at risk. These, however, must be implemented during the design phase of the boat itself, since they will have to take into account the shape of the hull and many other small factors that will influence the actual choice of the best solution for that specific case.
Going into the details of these solutions, we have already talked about many of them in some articles dedicated to them exclusively. For this, in the list below I will also add any links for those wishing to learn more about the subject:
- The basic rule when designing the cathodic protection of a boat is to choose the positioning of the sacrificial anodes in an appropriate manner, taking into account the profile of the hull and the parts to be protected.
- In general we will try to install sacrificial anodes with hydrodynamic shapes and geometries, so as to reduce the actual hydrodynamic impact of them. We also talked about it in the Anode of the Week 46 (dedicated to anodes for fast boats) and in the Anode of the Week 47 (dedicated to hydrofoil anodes).
- An extreme solution, but very effective if feasible (which is not always possible), is to create recesses in which place the anodes. This, moreover, limits the hydrodynamic problems on the anodes to a minimum. We talked about it in this Tecnoseal Answers.
the NACA01 prototype that presents some differences from what will be the final product
A Research in Continuous Development
Such solutions rarely allow us to obtain a relationship between anodes/performance that is absolutely in favor of both, but research and development of new technologies regarding this field continues constantly every day. Tecnoseal, for example, has developed a particular type of hydrodynamic anode (Cod.Tec.NACA) of which we had spoken in depth here.
Although the first Tecnoseal hydrodynamic anode has a few years behind it, its development and improvement have not stopped in the slightest. In these days a new version has been introduced that weighs only 1 kg (Cod.Tec.NACA01) which will protect parts of the boat in which the dynamics has a fundamental importance. Furthermore, when using hydrodynamic profiles, you have to be very careful to calculate the maximum protection times because in these cases the consumption of the anode is a bit anomalous and, in the parts where there is less mass, there could be interruptions in the electrical circuit created between the boat and the anode itself.
Summarizing what was said in today's article, yes, the sacrificial anodes installed will influence the performance of your boat by generating an anode/performance ratio that you will have to try to balance to choose the best solution for your situation. As we have seen, there is still no absolute way to obtain a maximum result in both fields, but there are numerous solutions that allow us to obtain excellent results, although we still have to sacrifice something in return.
One thing that, however, it is good to memorize, is that this choice of the best solution cannot be implemented lightly, but must be accomplished during the design phase of the boat. It is a complex choice that must take into account many different factors, not only of the shape of the hull, but also of how this is structured and how it will behave in the water. Making a rash decision can be expensive and, therefore, it is always good to turn to someone with experience in the field of cathodic protection!
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Tags: Tecnoseal, Hydrodynamic anode, tecnoseal answers, Basic Notions, cathodic protection, resistance to motion, drag, hydrodynamic, sacrificial anodes, hydrofoil, fast boats, recessed anodes, fast hulls