Abstract
To date, the high temperatures (above 140°C) met in some fields in, e. g. , the North Sea, impose the development of innovative corrosion protecting coatings. Thermostable products have been developed from combining a high-Tg thermoplastic and epoxyamine monomers (the latter reducing the viscosity of the former to allow processing) which, together with the associated coating process solve these services innovatively. Details of the subtleties of material choice and behavior, process engineering and how environmental issues are met are presented. Data from various long term ageing tests performed on these thermostable materials, including filled formulations, are discussed. Durability tests against sea water over 12000 hours at 160°C are followed by desorption and dynamic mechanical analysis to assess whether any irreversible degradation has occurred. Carbon steel adhesion measurements are carried out in the view of coating applications as well as in situ Tg values evaluated by impedance spectroscopy. Plasticization effect of water is discussed. In addition, impedance spectra also indicate the quality of corrosion resistance achieved under accelerated ageing conditions.
Highlights
Offshore pipe lines devoted to oil transport are externally coated with organic material for several reasons
Three main benefits should be underlined: – the reactive extrusion process uses a classical twin-screw extruder allowing to blend thermoplastic and thermoset precursors at minimum cost, while respecting the requirement T < 250°C; – blending and coating technologies are non polluting processes in respect with environmental requirements— Volume Organic Compounds (VOC) = 0%, and non toxic filler/pigment); – the crude compound thermoplastic/thermoset can be cut into pellets after the first extrusion, extruded a second time in band to coat a tube
An alternative process of application is based on the micronisation of pellets for a final powder application
Summary
Offshore pipe lines devoted to oil transport are externally coated with organic material for several reasons. The main one is to protect the steel against corrosion to sea water. Pipe coatings impart protection against mechanical damage or disruption occurring when a flow-line is being installed and throughout its life on the sea-bed. Offshore infrastructures are required to operate in extreme conditions, since they may be exposed to temperature above 140°C (for example high temperature fields in North Sea). External pipe coatings should provide continuous corrosion protection in service conditions, meaning that the coating material has to exhibit stability in sea water and adherence on steel beyond 140°C. Organic coating material should be processed under 250°C in order to avoid changes in steel microstructure, while respecting environmental requirements. There is a need in organic coating material and process to overlay actual technical limitations
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