Protection of underground piping network in congested petrochemical plants is one of the major problems when cathodic protection is applied for its protection from the soil side corrosion. Process equipment reinforced concrete foundations and electrical plant grounding are integral part of a plant. Not only a significant amount of protective current is consumed by these elements, but also, they restrict the flow of protective current to the intended structures from a remote ground bed. Similarly, large diameter pipes shield small diameter pipes when shallow and closely distributed anodes are installed.
Corrosion is a naturally phenomenon commonly defined as the deterioration of metal because of a reaction with its environment. Corrosion occurs as a result of an electrochemical reaction driven by a potential difference between two electrodes, an anode and a cathode, connected by an electrolyte Water or Soil.
If corrosion isn’t mitigated, dangerous, and expensive damage can be the result.
Cathodic protection is the most common electrochemical technique used to prevent corrosion on buried metallic structure coating or not to the soil.
Protection is accomplished by applying a direct current to the surface of the metal, which causes the electrochemical potential of the structure to shift from a corroding state to a polarized and non-corroding state. Cathodic protection intent to polarize our structure to a minimum potential of -800 mv, for carbon steel.
On complexes structures to achieve Cathodic protection electrical continuity and electrical isolation is two conditions where need to consider during our design to decide which part need to protect. Also, external coating is another one important parameter.
To perform a detail, design the below parameter is necessary to consider
- Structure details
- Electrical isolation
- Foreign electrodes
- Interference assessment
Cathodic protection can be achieved by three methods.
- Using impressed current ground bed (s) sufficiently remote from the complex structure to be protected (conventional ground bed). By using this method, high levels of cathodic protection current are often required because all components of the complex structure receive and consume current.
- Using distributed or continuous ground bed (s) located along and close to the structure to be protected. The purpose of this method is to localize the application of cathodic protection current to the structure to be protected.
- By a combination of the above two methods.
Basic components of our Cathodic protection system are
- Transformer rectifier
- Anode ground beds
- Negative connection
- Test Station
- Earthing system
- Electrical safety bonding (Permanent and Temporary)
- Electrical continuity
SYCHEM SA working more than 30 years in Cathodic protection doing design, supply materials, installation and commissioning’ trying to deliver some of most complex project in the world, on budget and on time for our clients.