New Pipeline External CoatingPurethane coating’s high electrical resistance combined with low Cathodic Disbondment, high impact and abrasion resistance make it an excellent choice for pipeline external coating. This combination of electrical resistance and mechanical strength in a single monolithic layer makes it unique amongst all pipeline coatings.
The variable chemistry of 100% Solids Polyurethanes allows customised formulation of pipeline coatings with properties dependent upon end user requirements. These range from instant set, unprimed, hard, shop applied coatings to primed, slower set, site applied coatings with very high impact and abrasion properties.
Purethane coating are spray applied, seamless monolithic coatings which cure rapidly even at low temperatures. No pre or post heating or after treatment is required.
Pipeline coatings like 3 layer Polyethylene (3LPE) rely on an inner Epoxy coating which provides corrosion protection / electrical resistance and an outer Polyethylene coating which provides mechanical protection to the brittle inner coating. A copolymer bonds the two layers together. The differing chemistry and inert nature of the Polyethylene makes the mutual bond uncertain. Many long term performance reports suggest disbonding in service. Fusion Bond Epoxy (FBE) on the other hand is very brittle and requires very careful handling during installation. Both coatings require elaborate production plants and processes.
Purethane® coatings have excellent corrosion protection/ electrical properties as well as outstanding mechanical toughness in a single monolithic coating. Field joints, a weak point in other coating systems, are a continuation of the pipe coating with no discernable discontinuity between the morphology of the pipe coating and the joint coating.
Desired properties of an external coating for buried service, identified by NACE International RP 0169-94 are listed below:
- High Electrical Resistance
- Low Permeability
- Mechanical Properties to withstand damage during transport, handling , laying, bending , testing and back filling :
- High Adhesion
- High Impact Resistance
- Flexibility & Elongation
- Resistance to Cathodic Disbondment
- Physical stability and chemical resistance to prevent deterioration during design life
- Cohesive Strength To Prevent Cracking
- Resistance To Cold Flow & Thermal Stresses
- Resistance To Soil Stresses
Technical Bulletin elaborating the implications of these properties and comparing test results of Purethane® with other external coatings now available. Ask for a copy (Acrobat File) by E-Mail !
Minimum standard for 100% Solids Polyurethane Coatings are prescribed in DIN EN 10290:2004 “Steel tubes and fittings for onshore and offshore pipelines - External liquid applied polyurethane and polyurethane-modified coatings” and American Water Works Association / American National Standard Institute ANSI / AWWA C-222-99 “ Polyurethane Coating For The Interior & Exterior Of Steel Water Pipe Fittings”.Purethane coatings comply with these standards.