This Recommended Practice (RP) has been prepared to facilitate the specification and execution of coating work. While the requirements and recommendations are general, the document contains advice on how amendments can be made to include project specific requirements and requirements/guidelines by a regulating authority, or to reflect the pipeline operator's general philosophy on pipeline corrosion control.

This RP covers the process of applying external coating systems for corrosion control of submarine pipelines at the coating plant, and includes the qualification and implementation of this process. The following coating systems are covered:

1) Single or dual layer fusion bonded epoxy*).

2) 3-layer coating based on an inner layer of fusion bonded epoxy (FBE) applied by spraying, an intermediate adhesive layer applied by spraying or extrusion, and an outer jacket of polyethylene (PE) applied by extrusion*).

3) 3-layer coating based on an inner layer of FBE applied by spraying, an intermediate adhesive layer applied by spraying or extrusion, and an outer jacket of polypropylene (PP) applied by extrusion.

4) Multi-layer PP coatings with the 3 innermost layers as for 3) above and a relatively thick layer of foamed or syntactic PP for the purpose of thermal insulation plus an outer jacket in PP.

5) Glass fibre reinforced asphalt enamel coating*).

6) Glass fibre reinforced coal tar enamel coating*).

7) Polychloroprene (vulcanised rubber) coating (sometimes applied for thermal insulation in addition to corrosion control and mechanical protection).

8) Multi-layer polychloroprene (vulcanised rubber) coating (primarily for heat/thermal insulation).

*) Primarily for use in combination with a concrete weight coating.

Guidance note: Pipeline operators (and installation contractors if applicable) should consider the needs to carry out qualification of generic coating systems for specially demanding applications; e.g. resistance to bending during installation by reeling and long term (>10,000 hrs) thermal degradation of critical coating properties associated with high operating temperatures. Purchasers of linepipe coating should further consider pre-qualification of the coating manufacturers prior to the issue of purchase document.

This RP covers primarily the process of coating of ordinary pipe joints, and pipe joints with a buckle arrestor. It may also be used for coating of pipeline components (e.g. bends, tees and reducers), or for coating of linepipe for onshore pipelines, using the same or similar coating systems. The user shall consider the needs for amendments and deviations for such applications.

The following activities associated with linepipe coating are not covered in the present recommended practice:

— Requirements for the qualification of supplier specific coating materials for general purposes (i.e. not project specific), see Guidance Note to 5.4.3.

— Detailed design of linepipe coating systems for project specific purposes (e.g. heat insulation, anti-buoyancy; see also Guidance Note to 5.4.2).

— Application of concrete weight coating.

Although considerations related to safety and environmental hazards associated with either pipe coating work or properties of the coating in the ‘as applied' condition (reflected by national and multi-national regulations) are of great importance, such are never-the-less beyond the scope of this document.