Frequently Asked Questions
1. What is corrosion?
Corrosion is a normal occurrence common to all metals not in their natural state. The process itself is electrochemical in nature, very similar to a battery, where electrons flow between anodic and cathodic sites on metals. For corrosion to occur four elements are required:
*Anode – site where corrosion occurs and current flows from.
*Cathode–site where no corrosion occurs and current flows to.
*Electrolyte – a medium capable of conducting electric current (i.e. soil, water or concrete).
*Metallic Path – connection between the anode and cathode.
2. What is cathodic protection?
Cathodic Protection (CP) is defined as the reduction or elimination of the corrosion process, by making the corroding metal a cathode via an impressed direct current (DC), or by connecting it to a sacrificial or galvanic anode.
Impressed current cathodic protection - This type of cathodic protection system is typically applied to concrete balconies. The anode is installed as a titanium mesh beneath porcelain or ceramic tiling or as a ribbon mesh in slots in the concrete deck. The mesh anode distributes a protective current to the reinforcing steel with the help of a rectifier and provides for anodic reactions to take place in lieu of the reinforcing steel.
Galvanic cathodic protection – A sacrificial or galvanic anode system for reinforced concrete uses a more reactive metal (anode) such as aluminum or zinc, to create a current flow. Direct current is generated by the potential between the anode and the reinforcing steel that it is connected to. The sacrificial anode will corrode during the process and is consumed.
3. How do we know cathodic protection works?
CP has been in use for decades to protect underground pipelines, ship hulls, offshore oil platforms, underground steel storage tanks, bridges and many other structures that are exposed to marine or corrosive environments. In 1973, the first steel reinforced concrete bridge deck was retrofitted with CP to stop corrosion. Today, that bridge deck shows no signs of decay in the protected areas.
4. Describe the installation of the impressed current system?
Utilizing the impressed current system to protect balconies involves laying a titanium anode mesh over the repaired concrete deck, which is then covered with a thin topping or thinset. A tile overlay may be installed over the mesh depending on the owners’ choice of finish. If a tile cover is not desirable, a titanium ribbon mesh can be inserted into saw-cut slots in the balcony deck and filled with a non-shrink cementitious grout. The concrete surface is then painted or sealed with a waterproof membrane. A power supply (rectifier) is used to convert alternating current (AC) to direct current (DC). The rectifier and associated junction boxes are typically installed in a utility room. The anode system is connected to the positive pole of the rectifier using wire in conduit and the rebar to the negative pole.
5. The entire rehabilitation project is supposed to take one year. Will the CP system installation impede the completion date for the project?
The CP system is typically installed simultaneously with other repair work. In general there should be no increase in completion time for the restoration project if CP is included in the scope.
6. Is there any maintenance to the CP system?
Once the CP system is installed it is necessary to provide routine operation and maintenance. For impressed current systems this involves visual inspection of the system and periodic checks. New advancements in technology, such as remote monitoring systems which are available from Corrpro, have provided a convenient way of maintaining CP systems.
7. What is the cost savings overview?
Cathodic Protection Systems provide considerable technical and economic benefits over traditional, remedial approaches. In five to seven years CP will have paid for itself by preventing future concrete repairs, which are typically required every five to seven years. Also, installation costs for CP are typically 10-20% of the replacement cost of a balcony.
8. Can project costs be minimized if the owners purchase their own tile, screens, shutters and arrange for installation separately, or would this interfere with the CP system installation and project scheduling?
From logistical and practical standpoints, this type of approach would save very little money. Interference with the scheduling and restoration places constraints on contractors and can slow down the completion of the project.
9. Can the tile on the balconies, once reinstalled, be removed and new tile installed without damage to the titanium anode mesh underneath?
This may be possible. Consult Corrpro first before attempting to replace any tiling over titanium anode mesh.
10. Is the electricity controlled centrally and continuously? How much electricity will the CP system use?
Yes, the rectifier and remote monitoring system are connected through one circuit breaker, and the system is in continuous operation (24-hrs. per day). Surprisingly, very little energy is used. The electric power required to protect 10,000 ft2 of concrete is typically equivalent to operating one 25-watt light bulb continuously.
11. If the condominium gets struck by lightning, will the system get destroyed?
The rectifier is equipped with upgraded lightning protection, which helps protect against lightning strikes. The titanium anode mesh system in concrete is relatively stable and will not suffer damage if the building is hit by lightning. To date we have had no problems with our system on condominiums from power surges or lightning strikes.
12. Will the CP system affect my TV reception or pace maker?
The CP system produces a low voltage direct current. Voltage levels are typically very low (1-2 Volts DC) which is similar to a battery. Because of the low voltage and current levels, TV reception is not affected and there will be no hazard to your health.
For more information contact Clem Firlotte at Corrpro’s Concrete Services Group at:
330-723-5082 x.407
or email:
cfirlotte@corrpro.com