PRODUCTION • PROCESSING • HANDLING
corrosive environment, can affect all types of welded connections on drill ships, drilling and production rigs and platforms. With an issue as important in terms of both cost and productivity, we cannot afford to think in terms of rectification. We are, instead, looking at surface engineering – the treatment of material surfaces to change their properties or characteristics to achieve improvements in performance – eliminating corrosion by design. When considering offshore and subsea components, engineered surface coating solutions can be employed to achieve, amongst other things, improved corrosion and wear resistance. As such, it is a discipline that should be applied throughout the design, specification and manufacturing process as an integral part of component development to ensure that the specific needs of the operational environment are addressed. Although corrosion is inevitable, it can be inhibited by the application of specialist engineered coating solutions to extend the service life of components and control maintenance costs. Steps taken at the product finishing stage will minimise the risk and effects of corrosion and so optimise performance and longevity. Although there are a number of options, including changing the environment by the use of inhibitors, cathodic and anodic protection – even using more highly alloyed specialist stainless steels – the application of corrosion-resistant coatings is perhaps the most widely used way of protecting steel. Te choice of coatings includes organic, metallic or inorganic and there is a wide variety to choose from. Specialist engineered coating solutions can address issues of corrosion, gall resistance or fouling problems. Applications typically include Christmas trees, subsea connectors and seals, riser systems, clamps, seat, seals and valves, hangers, threaded components such as nuts and bolts, as well as manifolds and valve bodies.
COATING OPTIONS OFFSHORE Termal spray coatings exhibit high resistance to corrosion and wear in extreme applications and are increasingly
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being used in the oil and gas industry. Te use of thermal spray to apply coatings, such as high velocity oxy fuel (HVOF), is one of the most commercially viable and allows the control of various parameters including powder particle velocity and temperature, which influence coating properties such as residual stress, bond coat strength and microstructure. Another coating system used to provide
corrosion resistance, often to offshore structures on-site, is wire arc spraying. Wire-arc thermal sprays provide a dense and strong metal coating and they are an excellent choice for protection against corrosion. Galvanically active coatings such as zinc and aluminium can be applied using the wire-arc process. Te wire-arc process involves two wires
that are driven into an electric arc to form molten particles of spray and are forced out of the gun by compressed air onto the substrate. Te process is known as a ‘cold’ procedure, as the substrate temperature can be kept low throughout. Wire-arc metal spraying is also used to apply non-slip coatings to protect both infrastructure and employees and is typically applied to walkways and tread plates. Termal spray aluminium (TSA) is also applied using a wire-arc spray gun. Fluoropolymer coatings are a blend of high performance resins and fluoropolymer lubricants, such as polytetrafluoroethylene (PTFE). Tis
Hostile environments require advanced levels of corrosion protection
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