Ageing of internal coatings in pipelines

Site last update July 15th_2021

Newly applied internal coatings

Chapter 1 (Flow Friction theme) addressed more specifically the newly applied internal coatings in order to determine their surface characteristics (profile) and their aerodynamic benefit relative to an uncoated internal wall (bare steel). Regarding surface characteristics, chapter 1 shows the relative impact of deformations with short wavelengths (roughness) and those of longer wavelengths (ripple) encountered with certain types of coating (in particular water solvent based epoxy). Regarding the aerodynamic impact of the material itself, chapter 1 highlights the positive contribution of some coating materials (epoxy, polyamide, etc.) facilitating the transport of gas. This last aspect has been defined by the terminology “Parietal sliding”.

Coating aerodynamic properties and testing in severe conditions

Aged internal coatings

Chapter 2 (pipelines theme) focuses more specifically on the ageing of internal coatings to assess the impact on aerodynamic properties. The types of ageing more particularly studied relate to rapid decompression, erosion and the physiochemical interactions between the coatings (solvent and water based coatings, polyamide) and certain chemical agents encountered in the transport of gas, such as the injection of tri ethylene glycol. This study shows a deterioration in the aerodynamic performance for certain aged coatings, particularly at high Reynolds number (small boundary layer), although the surface characteristics (profile) have not been altered. The modification of the aerodynamic performance would be explained by a chemical change at the coating surface (adsorption). For certain aged coatings the performance degradation could be explained by a “Parietal slow down”. This effect is the opposite to the one encountered with new coatings with “Parietal sliding” or “Parietal induced acceleration”.

A Detailed document will be provided later