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Facts About Impressed Current Cathodic Protection (ICCP)
The cathodic protection current of an Impressed Current Cathodic Protection (ICCP) system is obtained from an external source such as the local utility company which can impose a current sufficient to counteract the existing currents of the corrosion cell. The current is "impressed" on the corroding structure through the use of relatively inert anode materials.
Typically an impressed current cathodic protection system for a concrete structure will contain the following components.
DC Power source
Inert anode material
Wiring and conduit
The local utility is the most common source of external power for the system. This is of course AC current and must therefore be converted to DC current for use in the CP system. Rectifiers are available in a variety of sizes and types to satisfy the needs of all corrosion prevention situations.
Anode material in an ICCP system is a relatively
Advantages of Impressed Current Cathodic Protection (ICCP)
Impressed current cathodic protection was first applied to a bridge deck in 1973. Today that structure shows no signs of deterioration due to corrosion. Such long term corrosion control combined with advantages listed below make ICCP a wise choice.
The Solution: Cathodic Protection Treats Cause
The Federal Highway Administration has found that cathodic protection is the only proven technology for stopping corrosion once concrete is contaminated with salt.
In many cases the best and most economical solution is a cathodic protection system installed by specially trained NACE certified corrosion specialists at Southern Cathodic Protection Company.
Conventional concrete repair methods typically treat the symptoms, but not the cause of corrosion damage. Removing delaminated concrete and patching does not address the chloride contamination or lower the pH in the adjacent concrete. In fact, patching often results in a new corrosion cell in areas next to the repair work. This can actually accelerate corrosion and within a few years, significant concrete damage can occur. Meanwhile, corrosion continues to weaken the rebar.
A variety of maintenance options are available for corrosion damaged bridges
The Problem: Corrosion of Steel in Concrete
More than $5 billion is spent each year to repair and rebuild concrete structures damaged by corrosion of reinforcing steel. This damage is seen every day on bridges, buildings, parking ramps and other steel-reinforced concrete structures.
The Cause: Contamination
When first poured and cured, concrete provides a friendly environment for steel. But it can turn hostile over time as several substances penetrate the concrete. Carbonation occurs when carbon dioxide enters the concrete, reacting with the lime and lowering the pH. In addition, chloride ions from deicing salts or salt-laden air can combine with water and oxygen to create a corrosive environment. An electrochemical corrosion cell is established and the process of delamination begins. As the rebar corrodes, rust forms and takes up more volume than the steel it replaces. This puts expansive forces on the concrete, which ultimately lead to cracking, spalling, and delamination of the
Advantages of Cathodic Protection
When cathodic protection is the right corrosion control method it has both technical and economic advatages. These advantages stem from the fact that cathodic protection is a simple yet elegant application of fundamental laws of nature.
An Introduction to Corrosion
Corrosion is an electrochemical reaction based on universal laws of nature. All metallic structures corrode. It is just a question of how quickly.
Steel, for example, is a man made substance produced from iron oxide. The energy added in the refining process is unstable. Given a suitable environment, steel will release this energy and return to its natural state of iron ore. When immersed in an electrolyte, such as soil, water, or concrete, metals produce a current which causes ions to leave their surface. The rate of current flow determines the life of the structure. One ampere of current consumes approximately 20 pounds of iron per year.
The job of the corrosion engineer is to slow down or halt this process. Included in the techniques available are material selection, coatings, inhibitors and cathodic protection.
The area of metal where current is discharged and corrosion occurs is called anodic relative to the cathodic or noncorroding areas. By