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Corrosion resistant alloys (CRAs) are used for many pipeline and wellhead components associated with oil and gas production environments but may be considered too costly for longer crude oil and natural gas production lines. Mitigation of internal corrosion for these types of pipelines is normally carried out by batch treatment or continuous injection of corrosion inhibitors, especially the surfactant type of organic inhibitors, which are more economical than using a CRA.
Organic surfactant-type corrosion inhibitors are widely applied in the oil and gas industry considering their high efficiency at low ppm concentrations. The investigation of organic inhibitor adsorption and inhibition mechanisms on carbon steel has been limited by the difficulties with surface characterization techniques at a molecular level. Atomic force microscopy (AFM) can provide localized visual observation, and can also achieve characterization of mechanical properties of an inhibitor film, through friction and surface stiffness measurements in multiple operational modes. Reported research has systematically studied the frictional properties of self-assembled surfactant monolayers on mica using lateral force microscopy. However, there has been no such studies done on carbon steels. In the work reported herein, in situ AFM topography measurements in contact mode, in situ AFM friction imaging and in situ AFM phase imaging techniques have been applied to investigate the influence of different microstructures present in a ferritic-pearlitic carbon steel on inhibitor adsorption mechanisms as well as corrosion inhibition of CO2 corrosion. AFM c friction images show a large friction contrast between inhibitor covered cementite structures and ferrite structures, while in the absence of inhibitor this friction contrast almost disappears, indicating the inhibitor adsorption induced this difference. AFM phase images indicate no preferential adsorption of inhibitor on cementite or ferrite structures. These results indicate that either the adhesion force of inhibitor molecules on the cementite structures could be much smaller than on ferrite structures, or the molecular orientations of inhibitor molecules adsorbed on the cementite and ferrite structures could be different. In either case, it is hypothesized that the carbide component of the steel microstructure directly influences inhibitor adsorption, which could decrease inhibitor efficiency in ferritic/pearlitic regions and areas where iron carbide is more prevalent.
In this paper, a case study is presented for a marine structure for which modelling has been used to predict the protection potentials over the life of the structure.
The aim of any digital transformation of integrity management and in particular corrosion control is the improvement of communication efficiency, planning efficiency and maintenance efficiency. Key issues are predictive maintenance and clarity of the information available so engineers can make informed decisions. Therefore it is not just a question of collecting more information but also the way that information is used and shared with the decision-makers.
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Duplex stainless steels (DSSs) are based on the Fe-Cr-Ni system and are constituted of 30 to 70 % ferrite and austenite. They combine high tensile strength, good toughness, weldability, and excellent corrosion resistance including stress-corrosion cracking and resistance to localized corrosion.1-3 DSSs can be classified according to the Pitting Resistance Equivalent Number (PREN = Cr + 3.3 Mo + 16 N) in lean duplex (PREN= 22-27), standard (PREN = 28-38), super duplex (PREN = 38-45) and hyperduplex (PREN > 45).
Inline cathodic protection current mapping is a unique method of assessing a pipeline’s cathodic protection. This is accomplished by measuring the actual current received by the pipeline continuously along the entire pipeline length. Unlike pipe to soil potentials, which can have a great deal of error in them due to forces often beyond our control, the CP mapping tool uses the physical properties of the pipe itself to measure the CP current. The pipe is a very stable part of the circuit, unlike the soil surrounding it.