Numerical modeling of stresses relaxation phenomena in the complex assembly steel pipe/three layers polyethylene coating

Three-layer coatings are highly used to achieve long-term protection against corrosion. The coating is composed by a thick polyolefin topcoat, a modified polyolefin adhesive and a fusion bonded epoxy. Many observations suggest that significant internal stresses are present in the coating. Moreover, internal stresses in organic coatings can generate loss of adhesion and decrease the lifetime of the assembly. The aim of the study is to simulate relaxation phenomena during storage phase and to quantify residual stresses, in order to appreciate if they are critical for adhesion and sustainability of the assembly. During this stage, polyethylene or epoxy are able to relax all or a part of internal stresses as it necessarily occurs with any polymer.