Advanced Two Layer Polyethylene Coating Technology for Pipeline Protection

Oil and Gas pipelines are protected by various types of external coatings in conjunction with CP systems. Polyethylene is commonly used as the top coat in two or three layer systems. The existing two layer system found in the North American and Australian markets uses an adhesive that is mastic-based. It provides excellent corrosion resistant properties and has relatively low shear resistance in the adhesive layer, particularly at higher temperatures. The three layer system uses a copolymer adhesive to provide excellent shear properties and an epoxy layer which provides corrosion resistance. Both are excellent coatings when used in the proper environment. The major differences between the two systems are the mechanical properties at higher temperatures and the cost. The intention of this paper is to introduce a new system that bridges the gap in cost and performance between the two existing products. The new coating uses a hybrid adhesive which combines both the mastic and the copolymer functions, hence providing excellent corrosion resistance and adequate shear properties to withstand pipe movement and significantly reduce stockpiling and handling problems in high climate temperatures. The paper presents both the laboratory and plant production results and compares them to the properties of the other two existing coatings.