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What is a visco-elastic coating?

The main characteristic of this coating material is the permanent visco-elastic behaviour. Due to this visco-elastic property, the system is able to self-healing small coating defects. Usually the basic raw material for a visco elastic coating is “PIB” . This is the acronym for polymerised isobutylene. It usually applied as a tape in conjunction with multiple layers.

This PIB coating material is widely used by the coating in the field of the circumferential welds and bends or as a coating repair system at damaged coating.  This coating system consists of 2 layers: The anti corrosive inner layer of polyisobutylene and a PVC based mechanical outer layer. PIB material is also used when smaller parts of a pipeline have to be coated for example where changes in the ‘Right of Way’ are necessary or in case of refurbishment of the external coating of pipeline sections.

Techniques to apply visco-elastic coatings

There are multiple techniques to apply visco elastic coatings. The first procedure, usually applied at small surface areas, is to do so by straight wrapping.

Straight wrapping of visco elastic coating

Another procedure, which is most commonly used is to wrap it by spiral wrapping

Spiral wrapping of the inner visco elastic coating

Usually, PIB is only applied as a barrier towards corrosion. An important property is that PIB will remain it’s elastic properties over time. Therefore a coating system usually consists of 2 layers: The anti corrosive inner layer of polyisobutylene and a PVC based mechanical outer layer.

Application of PIB outer layer, spiral wrapping

PIB material is also used when smaller parts of a pipeline have to be coated for example where changes in the ‘Right of Way’ are necessary or in case of refurbishment of the external coating of pipeline sections and the PIB coating system is also used when an irregular surfaces component should be coated properly. For example valves, flanges, tees

Applying the inner coating with visco elastic tape materials
Application of PIB outer layer at tee-formed surface

For many field coating application with tapes or sleeves, the pre treatment of the steel surface is essential for getting a good adhesion of the coating onto the pipe. The pre treatment of the steel surface using the PIB 2 layer coating system is less critical.

The coating system requires a surface preparation of ST 2/3 which can be achieved by hand tool / machine tool cleaning, or by means of abrasive blasting to cleanliness Sa-1 (brush or blasting) in accordance with ISO 8501-01.  Because of the adhesive properties, a surface profile as obtained by blast cleaning is not required.

You can find more information about the different surface preparation methods in this article

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