General Specifications

Reinforcing steel in concrete is naturally protected from corrosion by the chemistry of the concrete and the location of the steel in the concrete.  However additives to the concrete during placement, damage, cracking, water penetration, salts and other forces cause reinforcing to corrode.  The corrosion cycle is called the cathodic cycle and is based on a electrochemical process.  The corrosion causes the steel to expand from its original size and damage the surrounding concrete causing spalling and cracking.  The spalls and cracking cause more steel to be exposed to the harmful environment and more corrosion.  This is a seemingly never ending cycle of damage and more damage. 

This cycle can be broken by cathodic protection of the steel by two of methods - galvanic cathodic protection and impressed current cathodic protection.  Galvanic cathodic protection involves installing an anode into the electrochemical process.  The sacrificial anodes are made in various shapes using alloys of zinc, magnesium, aluminum or other alloys. The electrochemical potential of the anode, current capacity and consumption rate is higher then the reinforcing steel. Galvanic anodes are designed to have a more active negative voltage than the typical 60ksi steel reinforcing.  The corrosion reaction is halted when the alloy of higher potential is connected to the reinforcing steel.  The galvanic anode continues to corrode consuming the anode material. The polarization is caused by the current flow from the sacrificial anode to the cathode (reinforcing steel). The force driving the cathodic protection current flow is the difference in electrochemical potential between the anode and the cathode. In some concrete structures galvanic anodes can’t deliver enough current to provide complete protection. Impressed current cathodic protection systems use anodes connected to a DC power source called a cathodic protection rectifier.   Anodes for impressed current cathodic protection systems are tubular and solid rod shapes or continuous ribbons of various specialized materials. These include high silicon cast iron, graphite, mixed metal oxide, platinum and niobium coated wire and others.

The anode for the galvanic cathodic protection system can be solid bulk anodes or a thermally sprayed High Purity Zinc-see TOPCOR Metalizing.   Bulk anodes can be installed on the outside of the structure and electrically connected to the reinforcing steel.  They can be installed on the reinforcing steel and the concrete placed around them.  The amount and placement of the anode would need to be designed by an engineer. 
Key elements to the cathodic protection system are:

1. System design
2. Assurance of electrical continuity in the reinforcing steel
3. Installation of the anode
4. Installation of the negative connection plates
5. Inspection of the work
6. Repairs of the structure-see TOPCOR concrete repair
7. Commission and documentation of the system

For further information or for a site survey or estimate, please go to our contact us page….