The main characteristic of this coating material is the permanent visco-elastic behaviour. In other words it will stay in a high viscous fluid phase even after years of application. 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. PIB is amorphous and inert material, which has very little impact on the environment. It is therefore considered an environmentally friendly coating system. PIB also has very good anti-corrosion properties. This is because the adhesion between the substrate (iron) and the coating is very good.
It usually applied as a tape system, where PIB is placed on a backing layer, to make it easier to apply the coating on a substrate. Usually, PIB is used as a base layer directly placed on the substrate. On top of the PIB layer, another tape is used to protect agains mechanical and puncture impacts.
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. With this procedure, you create pieces of coating of equal length, which are placed around the pipe with an overlap.
Another procedure, which is most commonly used is to wrap it by spiral wrapping
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.
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
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.