What Does Two-Layer Extruded Polyethylene Coating (2LPE) Mean?
Two-layer extruded polyethylene coating (2LPE) refers pipeline protection consisting of two layers. The two-layer structure utilizes mastic-based adhesives and polyethylene copolymers. This offers top-notch protection against corrosion, especially at elevated temperatures.
Mastic-based bonding agents are comparatively inexpensive and offer impressive cathodic disbondment (CD) resistance. Also, these have low peel and shear strength and are limited to applications at low temperatures. On the other hand, two-layer extruded polyethylene coating bonded using copolymers provide excellent shear resistance and adhesion, but typically poor CD resistance.
Corrosionpedia Explains Two-Layer Extruded Polyethylene Coating (2LPE)
At present, pipelines in the water transportation, gas and oil industries globally are typically protected by coatings along with cathodic protection. One of the most common coating products is the two-layer extruded polyethylene coating that provides exceptional corrosion defense to pipelines.
Two-layer coating systems commonly involve two types of adhesives. The properties of the adhesives will dictate which type best suits the needs of certain industries. Each material has its own set of advantages and disadvantages:
Advantages of mastic adhesives:
- Low production cost
- Amorphous and pressure sensitive
- Forgiving to temperature application and surface preparation
- Acceptable CD resistance
- Great water repellent
- Easy application
Disadvantages of mastic adhesives:
- Low peel and shear resistance
- Lesser operating temperature
- Low soil stress resistance
- Copolymer adhesive advantages:
- High peel and shear values
- Elevated operating temperatures
- Better resistance to compression
- Excellent soil stress resistance
- Copolymer adhesive disadvantages:
- More difficult to apply
- Critical pre-heat surface
- Inferior wetting characteristics
- Necessitates perfectly cleaned and prepared surface
- More costly
- Poor CD resistance in absence of epoxy primer
Studies and experimentation are being performed to develop a hybrid adhesive that will possess the good qualities of both adhesives mentioned above. This will make the pipeline protection industry more competent in providing the necessary defense against pipe degradation.