Since the first CP (Cathodic Protection) projects have been carried out in the Netherlands, now almost 30 years ago. This specialist method of concrete maintenance has been further developed into a proven effective method for permanently stopping rebar corrosion. In addition, many possibilities have been developed based on this technique for use in all types of rebar corrosion in all market segments.
Causes of rebar corrosion (and application of cathodic protection)
In most cases rebar corrosion is often the actual cause of concrete damage. Other causes can usually be traced to chemical attack, mixed impurities in the mixture and external (mechanical) causes.
Cathodic protection and the different systems
Cathodic protection comes in many forms. The principle is based on reversing the current by introducing another anode that takes over the role of the dissolving reinforcing steel. As a result, the steel will end up on the protected side of the reaction so that it can no longer rust.
The European standard NEN-EN 12696 and the Dutch CUR Recommendation 45 set all kinds of rules for the application of cathodic protection systems. From the design, the measurements and inspections during construction and before commissioning, to the mandatory monitoring of the systems for 10 years after construction.
Two basic principles for cathodic protection
Cathodic protection has two basic principles, further explanation can be found in the headings below.
Galvanic cathodic protection
A galvanic system is based on the galvanic effect of the metals. Hereby the base metal sacrifices itself for the more noble metal. In fact, this is the same process as for galvanizing steel. Because this system actually forms its own battery, no external power source is required. This form of cathodic protection is applied as a surface anode. For example as a zinc foil on a conductive gel or as a discrete anode to be built in.
Cathodic protection based on imposed current
Where galvanic systems fail, for example with larger surfaces and higher rebar concentrations (with heavy structures), cathodic protection based on imposed current offers the solution to the corrosion problems of the concrete structure. An anode material is applied in this form of cathodic protection. Which is fed with a very small protective current through an external power supply. There are various methods for applying cathodic protection through imposed current. Conductive coatings, durable titanium strips, mesh and mesh anodes and various types of aperture anodes are examples of this.
Although we usually link the application of cathodic protection to the presence of high concentrations of chlorides in the concrete. Other very interesting applications of CP are also possible. These include:
- In strongly carbonated or porous concrete in an aggressive environment, with poor or costly access for example, applying a CP system on a preventive basis can provide a more economical alternative to maintenance.
- Incorporating it as a preventive measure in the new-build phase, you have a “dormant” system that is monitored. However, when higher current densities are measured the system is actually switched on when pitting corrosion becomes a real possibility. These types of solutions are also produced by a growing realisation that prevention is better than the cure, whilst they are also a strategic and economically justifiable option as part of a TCO approach.
The trajectory against rebar corrosion
The engineers and corrosion specialists of SealteQ investigate the problems, advise on the possibilities, design and specify the solutions and carry out the entire process for you in accordance with all the rules of the art. Including the maintenance, monitoring and reporting thereof in accordance with international regulations. With the application of CP you are 100% sure that no rebar corrosion will occur in the protected parts.
Our service, which is strongly focused on innovation and quality, offers our customers the certainty of a customized solution. With the application of Total Cost Management and the Total Cost of Ownership approach, we offer added value with your strategic maintenance management.