Corrosion of internal and external surfaces of pipelines is a leading cause of failure of buried pipelines. Apart from huge financial losses due to damaged assets, corrosion causes catastrophic failures, accidents and loss of precious lives. In case of potable water systems, corrosion can lead to disruption, wastage and supply of water of inferior quality.
Corrosion Protection of Buried Pipes
- Negligible permeability
- Good electrical and electrochemical resistance
- High adhesion to the pipe's surface
- Good impact strength.
- Scratch resistance and abrasion resistance, to protect against damage during handling, testing, transport, laying and other site activities.
- Not prone to cathodic disbondment.Resistance to changes in soil and thermal stresses
- Resistance to cracking
- Loose polyethylene jacketing
- Epoxy coating
- Bituminous coal tar based coatings
- Polyurethane coatings
Loose Polyethylene JacketingFor water pipes laid in corrosive sites like landfills, polyethylene encasements are commonly used. The advantages include ease of installation, low maintenance cost, low failure rates. However, the polyethylene encasement may get damaged during installation. It softens at 80°C (176°F) and melts at temperatures close to 100 to 110°C (212 to 230°F).
Bituminous CoatingFor ductile iron pipes of water systems, zinc spray-bitumastic coating is also used in combination with polyurethane or polyethylene jacketing. However, the combination is subject to failure due to scratch damage during installation.
Polyurethane Coating (PU)Polyurethane can be used for both internal as well as external surfaces. Coating can be completed during the pipe manufacturing stage itself. Zero VOC polyethylene and epoxy coatings are also being offered.
Advantages of Polyurethane (PU)Well-designed solid polyurethane reduces the load current of cathodic protection (CP) systems.
Zero VOC PUZero VOC polyurethane coatings used for buried pipelines are an example of new coatings developed due to regulatory requirements. These coatings are used for:
- Water and wastewater piping systems,
- Oil and gas piping
- Industrial applications.