Transportation of hydrocarbon is often accompanied by sand particles, water and acid gases which can induce erosion and corrosion phenomena in the metallic components and pipelines. Nickel-Phosphorus (NiP) alloys obtained through chemical plating offer a significant solving route for protective coatings, by providing increased hardness, erosion resistance and corrosion protection. In addition, electroless NiP deposition allows low production costs and effectiveness in large components with complex shapes, with a good adhesion between the composite coating and the metallic substrate. Multilayer coatings permit then to further increase corrosion resistance.
This paper presents an innovative NiP Multipurpose Multilayer Coating (MMC), developed by Eni in cooperation with Politecnico di Milano (PoliMi), whose performances can be tailored by: 1) choosing the appropriate concentration of phosphorus to obtain corrosion resistance; 2) multilayers to improve resistance to corrosion in aggressive environment; 3) rigid microparticles addition to further increase the hardness of the matrix and achieve higher resistance to erosion.
Several tests were carried out in the laboratories of PoliMi and EniProgetti to optimize the composition of the MMC: erosion and abrasion resistance, corrosion resistance in a flowing sour environment, morphology, micro-hardness and texture roughness of the different types of coating. The experimental activity allowed to characterize the behaviour and to identify optimized compositions of MMC.
Finally, optimized MMC have been validated with in field real tests by applying the deposition process both by immersion, in case of small components, and by fluxing, with an in-situ apparatus specifically designed for pipes.
In the Oil & Gas industry, transportation of hydrocarbon products is often accompanied by sand particles, water and acid gases which can induce erosion and corrosion phenomena in the metallic components and pipelines. The consequences of such phenomena are the malfunction of metallic equipment and lines and the reduction of their useful life; this therefore entails considerable economic losses for industries. These losses are primary due to two reasons: the fact that continuous maintenance (or replacement) of the affected equipment is required, and because the damage could lead to an obligatory interruption of the normal operating activity of the plant, thus causing loss of production. As an example, in the UK alone, the Department of Commerce and Industry in 2000 estimated the cost of erosion damage to be around £ 20 million per year, while, according to a NACE study, the total annual cost of corrosion in the Oil and Gas industry is estimated to be $1.372 billion.