Corrosion Protection

Description

Why Fusion-Bonded Epoxy Coating?

There is an apparent lack of understanding of basic corrosion concepts relating to solid non-uniform electrolytes. There are two basic types of reactions that cause corrosion in steel:

• Galvanic
• Electrolytic corrosion

Both require a chemical reaction and the flow of electrons.

Corrosion in Concrete

The most common cause of corrosion in concrete are galvanic cells. This process requires either dissimilar metals in a uniform electrolyte which has an external return current path or one continuous metal in a non-uniform solid electrolyte, in this case a reinforcing steel bar in the concrete mix.

Prevention of Concrete Corrosion: Kill or Cure?

There are a number of procedures that can be utilized in the prevention of corrosion, but cost is always a major consideration not only in the initial cost of the prevention but also for maintenance and running costs.

Additives

Improving concrete with additives such as Microsillica, Pulverized Fly Ash (P.F.A.) and Hydrophobic Pore-blocking Ingredients (H.P.I’s), while having considerable effect on concrete strength and durability, compound the already existing problems with non-uniformity, partly due to the highly diverse ratio of additive to concrete.

Cathodic Protection

Although cathodic protection is a well-accepted principle with a very long history, great care must be taken to ensure that in active CP systems the initial protection current does not become the agent of early or rapid corrosion of the steel. Any cathodic protection system is only as good as the continued monitoring and deciphering of its performance. In the US and Canada, its use is limited and cannot be used in residential or commercial structures other than car parks.

The corrosion of reinforcing steel in concrete structure is attributable to a variety of factors, including the harsh climatic conditions (high temperature and humidity rates), temperature variations between indoor and outdoor environments, high salt content in the soil and air and high rates of vapor and gases in the vicinity of industrial facilities. These gases infiltrate through fine cracks in buildings, causing the steel to grow in size and expose the rebar to the elements, thus triggering the corrosion process, leading eventually to the total or partial collapse of buildings. The result is an increase in the cost of maintenance, or complete reconstruction, of buildings.

The Cost-Effective Solution

The protection of the steel itself within the concrete is one of the most cost-effective solutions. Applying an epoxy coating to the steel rebar significantly prevents corrosion. The coating provides a tough and inert barrier impervious to chloride and other salts, and is independent of the concrete changing.