Corrosion protection remains essential for screw piles, both for the threaded part and for the above-ground part.
Depending on the environment in which the piles are installed, the actions on their surface can be more or less aggressive. Generally, Eurocodes consider a loss of thickness of 0.01 to 0.04 mm per year. These values may seem very small, but in the long term they can damage the structure.
For this reason, it is essential to protect it using one of the methods described below.
Protection par surépaisseur
This type of protection simply consists of using a metal with a thickness that can be lost during the life of the structure.
Advantage: there is no special coating required as in other methods.
Disadvantage: it is only suitable for structures with a limited lifespan.
Galvanisation à chaud
Cathodic protection (either impressed current or sacrificial anode) can be summarized by the following diagram: an electrical current is imposed by the cathodic protection station between the pile (which is connected negatively to the protection station, like a cathode), and an anode (positive electrode) made of a material that does not degrade over time (titanium, magnesium, etc.).
The protection station is an electrical circuit that can be either manually or automatically adjusted. In the case of manual adjustment, the cathodic current must be changed each season, depending on the change in the electrical resistance of the soil.
In the case of automatic adjustment, a robotic controller takes care of changing the cathodic current without the need for operator intervention.
Hot-dip galvanizing according to the EN ISO 1461 standard consists of covering the surfaces of the piles with zinc by dipping them in galvanic baths.
Since the electrochemical characteristics of zinc are different from those of steel, the coating will degrade before the structural steel of the piles, and this process usually takes more than 100 years.
Advantage: the appearance is very nice and the solution is durable.
Disadvantage: the cost of this protection remains high compared to others.
Protection cathodique
Cathodic protection (either impressed current or sacrificial anode) can be summarized by the following diagram: an electrical current is imposed by the cathodic protection station between the pile (which is connected negatively to the protection station, like a cathode), and an anode (positive electrode) made of a material that does not degrade over time (titanium, magnesium, etc.).
The protection station is an electrical circuit that can be either manually or automatically adjusted. In the case of manual adjustment, the cathodic current must be changed each season, depending on the change in the electrical resistance of the soil.
In the case of automatic adjustment, a robotic controller takes care of changing the cathodic current without the need for operator intervention.
Frequently asked questions:
- Where does the station get the power from? Answer: either from the building’s domestic network or from a photovoltaic panel specifically designed for this purpose.
- Is there a risk of electrocution? Answer: no, because the two circuits are decoupled and the current on the piles is low.
The above diagram shows the impressed current cathodic protection system.
Advantages: the solution is less expensive than galvanization and quite durable in the long term.
Disadvantages: any electrical system can malfunction, and in the case of using the manual station, technician interventions are necessary.