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With the rapid development of China's economy, energy and transportation industries have developed rapidly, and more and more oil and gas pipelines and urban rail transit have been built and put into use. Urban rail transportation systems, such as subways or light rail, generally use direct current traction and backflow through the rail. Because the track is not completely insulated from the earth, it is inevitable that some electric current will be discharged from the track to the earth to form stray electric current, which will cause interference to the surrounding metal components such as buried oil and gas pipelines.
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The spread of disbondment or corrosion from a scribe or holiday in a coating film, for which the terms rust creepage or undercutting are used in this paper is an important mechanism of coating degradation. The mechanism of rust creepage has been well studied by several authors who concur that the mechanism is driven by electrochemical reactions15. The reactions occurring at the discontinuity in the coating (scribe or holiday) involve an anodic reaction in which iron is dissolved. Adjacent to the anodic region, under the coating, a cathodic reaction occurs in which oxygen is reduced to hydroxyl ions.
Coating standards specify the required surface conditions needed prior to coating. A maximum amount of soluble salts of 20 mg/m2 is widely adopted as acceptation criteria, according to standard NORSOK M-5011. However, meeting these requirements for thermal spray aluminium coatings (TSA) in offshore environments is challenging due to the ubiquitous nature of water-soluble salts.
Application of sour linepipes has expanded toward severe sour environment regions including higher H2S partial pressure conditions. In 2013, actual sour gas pipeline failure occurred due to SSC (Newbury et al., 2018). One of the possible root cause of SSC was assumed to be a formation of hard spots in asurface region of steel. Fairchild et al. investigated and proposed three hard zone formation mechanisms including carbon contamination, dual phase microstructure and heat transfer variation in a recent paper (Fairchild et al., 2019; Newbury et al., 2019).
In the oil and gas industry, long-distance transportation of petroleum and related products is usually carried out in large-diameter carbon steel pipelines. Water present with the oil, along with corrosive species such as CO2, H2S and organic acids, causes severe corrosion of the inner pipe walls.1 An effective method of controlling corrosion is to continuously inject corrosion inhibitors into pipelines conveying oil-water mixtures. As corrosion occurs on water wetted metal surfaces, corrosion inhibitor (CI) molecules form protective films which retard electrochemical reaction rates at the water-metal interface,2 thereby protecting carbon steel pipes against CO2 ("sweet") corrosion and H2S ("sour") corrosion. Most commercial CIs are a complex mixture of several compounds that contain surfactant-type active ingredients, such as imidazoline, amine, phosphate ester, and quaternary ammonium derivatives.
In sour (H2S) corrosion systems, a small amount of H2S can retard the general CO2 corrosion rate of carbon steel by forming a passive iron sulfide (FeS) layer [1], [2]. Environmental factors dictate the formation of protective or partially protective FeS layers on carbon steel surfaces. High H2S levels often result in stable films that reduce the corrosion rate, contingent upon the maintenance of the sulfide layer [2]. Conversely, in slightly sour systems, which initially form mackinawite (FeS) [3], the system has the potential to cause pitting and extremely high localized corrosion rates [2].
In spite of the current focus on promoting renewable energy, oil and gas will still remain the largest energy source to support energy demand by 2050. As the world’s 4th largest crude oil producer and 3rd exporter, Canada produces 4.97 MMb/d of crude oil as of 2020. As the depletion of conventional crude oil reserve, more efforts have been taken to economically exploit the unconventional resources including oilsands bitumen.
High-strength materials with excellent corrosion resistance and mechanical properties are highly sought after for use in light water reactor (LWR) type nuclear power plants (NPP). In western pressurized water reactors (PWR), nickel-base alloys are often the main structural materials for the steam generator (SG) tubes, while in Russian PWRs or water-water energetic reactor (VVER) high-nickel alloys, for example XH35BT (35 wt.% Ni), can be found in some primary side high strength applications, such as reactor pressure vessel internals (RVI).
A 2002 study estimated the annual cost associated with corrosion of gas pipelines to be around $5 billion. Corrosion of oil and gas pipelines continues to pose a major issue in the oil and gas industry due to the combination of brine produced with the oil and the type of acid gas present which can lead to significant internal corrosion. Oil and gas reservoirs can be separated into two categories, sweet and sour.