In the upstream production systems, the external corrosion management typically does not affect the definition of the whole gathering network system design. However, its role is crucial for the integrity of any steel structure.
The external corrosion is generally managed with external coatings or cathodic protection systems designed to provide a durable protection against corrosive environments (either onshore or offshore). Typical external coating materials are polypropylene, polyethylene (in case of polyolefin coating), fusion bounded epoxy (FBE) or, in specific applications, thermal sprayed aluminium (TSA).
In High Pressure and High Temperature (HP/HT) reservoir applications, usually located in deepwaters offshore where the ambient temperatures are low (i.e. high temperature gradient between inside the pipelines and external environment), the selection of a specific external coating material might have significant impact on the design specification of the installed hardware, with special focus on the pipelines. In fact, depending on different physical properties of the external coating technologies, those may introduce stronger or weaker insulating capabilities and will modify the pipelines U Value, which describes the capacity of the pipelines to exchange heat with the external environment (and consequently the design specification of the production network).
A Case Study is here presented where impacts on the pipeline design specifications based on the selection of different external coating technologies have been described. In particular, it is here shown how the application of coating materials with lower insulating performance, e.g FBE coating, can increase the heat exchange between the hot production fluid and the cold external environment, leading to faster cooldown of production fluid.
In this case, reduction in operating fluid temperature has been used to prevent internal corrosion issues (generally linked to top of the line corrosion), however it may also be used as mitigation of HP/HT related issues, e.g. lateral buckling. Main pros and cons of FBE applied as a standalone external anticorrosion coating have been described in this paper.
Wang, Yefei (Key Laboratory of Unconventional Oil & Gas Development, China University of Petroleum East China, Ministry of Education, P. R. China, School of Petroleum Engineering, China University of Petroleum East China) | Yang, Zhen (Key Laboratory of Unconventional Oil & Gas Development, China University of Petroleum East China, Ministry of Education, P. R. China, School of Petroleum Engineering, China University of Petroleum East China) | Wang, Renzhuo (Key Laboratory of Unconventional Oil & Gas Development, China University of Petroleum East China, Ministry of Education, P. R. China, School of Petroleum Engineering, China University of Petroleum East China) | Chen, Wuhua (Key Laboratory of Unconventional Oil & Gas Development, China University of Petroleum East China, Ministry of Education, P. R. China, School of Petroleum Engineering, China University of Petroleum East China) | Ding, Mingchen (Key Laboratory of Unconventional Oil & Gas Development, China University of Petroleum East China, Ministry of Education, P. R. China, School of Petroleum Engineering, China University of Petroleum East China) | Zhan, Fengtao (College of Science, China University of Petroleum East China) | Hou, Baofeng (School of Petroleum Engineering, Yangtze University)
A novel indolizine derivative inhibitor for acidization was introduced. It could exhibit effective corrosion inhibition at a much lower concentration without propargyl alcohol and shows economic and environmental advantages. From quinoline, benzyl chloride, and chloroacetic acid, two indolizine derivatives were prepared under certain conditions. These inhibitive indolizine derivatives were both synthesised from benzyl quinoline chloride (BQC), which one of the conventional quaternary ammonium corrosion inhibitors used for acidising. The target compound was purified and instrumental analysis methods including elemental analysis, high-resolution mass spectrometry (HRMS), and NMR were used to characterise the chemical structure. The inhibition performance of the indolizine derivatives in 15 wt.% HCl, 20 wt.% HCl, and mud acid (12%HCl + 3%HF) for N80 steel was investigated by weight loss measurement, electrochemical method (potentiodynamic polarization and EIS), and SEM surface morphology assessment.
When 0.1 wt.% indolizine derivative was added, the inhibition efficiency of N80 steel in 15 wt.% HCl at 90 °C increased to 98.8 % and 99.1 % respectively without the synergistic effect of propargyl alcohol: however, in terms of BQC, even at a dosage of 1.0 wt.%, the inhibition efficiency of N80 steel only reached 83.3 % under the same conditions. The novel derivative could impart an improved corrosion resistance effect. Compared with BQC, there are more active adsorption sites in the derivative and therefore the inhibitor could be better fastened to the steel surface. The firmly adsorbed inhibitors would thereby prevent the metal surface from making contact with H+ ions and finally increase the inhibitory effect. As a high-efficiency corrosion inhibitor, the novel indolizine derivatives may offer a new strategy for corrosion protection in acidising.
Magerstädt, Michael (ROSEN Group) | Raeth, Thorsten (ROSEN Group) | Rentmeister, Nils (ROSEN Group) | Lai, Larry (ROSEN Group) | Forster, Stefan (ROSEN Group) | Altmeppen, Rainer (ROSEN Group) | Sarvi, Ali (ROSEN Group)
Slurry pipes often are exposed to heavy wear at or around the 6 o’clock position. In oil sands hydrotransport and tailings, wear of steel pipes is much higher under erosion-corrosion conditions. Whilst a number of metallic wear protection solutions, e.g., alloys, hardened steels, or chromium- carbide overlays can significantly extend useful life of such pipes, their protective effect can be severely reduced if erosion-corrosion conditions prevail.
Internal coatings made from high-performance polyurethane elastomers often allow similar or somewhat longer life extension compared to such metallic solutions, at a much lower investment cost. Under erosion-corrosion conditions, however, these elastomer coatings last much longer than metallic solutions. Life extension factors of 2-10 have been observed in oil sands slurry lines.
A former disadvantage of polymeric internal coatings was the fact that non-destructive testing and monitoring methods used on steel pipes could not be applied. For almost three years now, “instrumentation spools” in oil sands tailings service have successfully been in operation. The internal coating contains sensors rendering it “intelligent” in that it measures its own wear, including information on actual wear location on the 360 degree circumference. No hole through the pipe wall is required for data transmission to the operator.
This presentation will describe high-performance polyurethane elastomer internal coatings, the intelligent coating system, and field experience with it.
Elastomers Resistant to Wear and to Erosion-Corrosion
In mining, but also in numerous other industries, wear of metal surfaces and particularly the highly detrimental effect of erosion-corrosion, cause high maintenance and repair cost. These effects significantly contribute to limiting useful life of equipment exposed to them. Prominent examples are mining equipment like slurry pipelines, truck beds, slurry pumps, flotation equipment, chutes, and hydrocyclones, Examples from other industries are tracks of chain vehicles (e.g., street repair machines), heavy duty rollers, cutting table surfaces, or snow plough blades.
In the pipeline industry, inline inspection (“ILI”) tools (“pigs”) as well as cleaning pigs bear disks or cups that are exposed to strong erosive wear as well. These disks or cups need to be made from an elastic material since their purpose is to seal the tool against the inner pipe wall to create a pressure differential in the product stream which will propel the pig through the pipeline. Essentially, the disk or cup material needs to combine highest possible elasticity, wear resistance, and tear propagation resistance whilst at the same time having enough mechanical strength to keep its overall shape and not distort in a way that product stream can bypass the tool. Figure 1 shows a selection of ILI tools with cups and disks.
Li, Wei (University of Kentucky) | Landon, James (University of Kentucky) | Irvin, Bradley (University of Kentucky) | Thompson, Jesse (University of Kentucky) | Nikolic, Heather (University of Kentucky) | Liu, Kunlei (University of Kentucky)
Corrosion mitigation is an important topic for amine-based post-combustion carbon dioxide (CO2) capture operations due to the desire to use less expensive but corrosion-vulnerable materials such as low carbon steels in the construction of a capture system. In this study, the corrosion behavior of carbon steel in an in-house solvent was investigated in a pilot-scale post combustion CO2 capture process. Carbon steel specimens were placed inside process units where corrosion problems were previously found in the stripper column and the CO2-rich amine piping. An organic compound was studied as a corrosion inhibitor and degradation inhibitor in a range of 0 to 1000 ppm. It was found that the use of this corrosion inhibitor effectively retarded the corrosion rates of carbon steel in both unit locations.
Anthropogenic carbon dioxide generation from the combustion of fossil fuels such as coal and natural gas is one of the main acid gases projected to contribute heavily to global climate change. 1-2 One effective mitigation option is to adopt post-combustion CO2 capture and sequestration, which is a process consisting of the separation of CO2 from industrial and energy-related sources by typically using aqueous solutions of alkanolamines, and then transporting pressurized CO2 to a storage location for long-term isolation from the atmosphere. It is well known that monoethanolamine (MEA) is a benchmark solvent for the commercial application of post combustion carbon dioxide capture systems because of its cost-effectiveness, high capacity for CO2, fast reaction kinetics, and high removal efficiencies. 3 However, documented results have shown that MEA is highly corrosive to steels in the presence of oxygen, H2S, and CO2. 4-6 This can directly affect the whole system efficiency as well as the economics from solvent losses, unplanned downtime, reduced equipment lifetime, and even injury or death due to the damage by corrosion of main components of equipment made of steel.
Petrochemical process plant construction materials deteriorate when the plant is in service. In consequence, planned maintenance is undertaken to repair and replace equipment when it is predicted or detected that the facility has sustained damage. Typically, the operating environment does not normally vary very much. However, from time to time, process conditions may change rapidly and unexpectedly, due to contamination by water or other impurities, which can result in severe and widespread damage to the materials of construction. One such example concerned a process plant operated by our company. In this instance, damage to a process heat exchanger could result in moisture ingress that, in combination with an anhydrous hydrocarbon process stream that contained hydrogen chloride, produced a highly corrosive downstream environment, due to ionization of the HCl, even though the bulk liquor stream was relatively non-conductive. The low conductivity of the bulk environment meant that conventional process and corrosion monitoring instrumentation was unsuitable to detect the onset of the fault condition or provide an indication of the likely corrosion rate. In consequence, it was desirable for corrosion combination of monitoring techniques to be developed that could detect changes in the service environment in real time in order to reduce the severity and duration of such attack. This paper describes the development of the monitoring approach, and in particular on the application of electrochemical noise analysis, which, in combination with certain process chemistry parameters, could be used to detect the onset of the fault condition and prompt timely remedial action in such complex and/or low conductivity hydrocarbon processing systems.
The maintenance management regime that is applied in petrochemical plants operated by our company is intended to ensure stable operation and to minimize downtime and repair costs. When implementing maintenance management, predictions of plant degradation are made, based on data from the literature, or from inspection results, or from plant tests. However, it is difficult to make accurate estimates of the degradation rate as the service environment in such plants is varied. Furthermore, the service environment may change, due to a failure in other equipment or as a result of operational error, etc. A timely and appropriate response to these sudden occurrence events is one of the key issues of concern for good operational control of petrochemical plants. In these processes, many organic solvents contain halides and while the processes normally operate without difficulty, severe corrosion can occur, for example, if a tube leak occurs in a shell and tube heat exchanger unit, which allows a small volume of moisture into the process stream where it is mixed with the process liquor, resulting in ionization of the halides. If the detection of the fault condition is delayed for any reason, the damage may extend to the whole facility and the consequences may be catastrophic. It is very helpful, therefore, if process surveillance systems can be developed that can quickly detect such abnormalities. An example in which combustibles leaked from the damaged section of a process plant is shown in Figure 1. The release resulted in a fire accident on an organic solvent process unit, which involved a solvent release that contained halides. In this case, moisture from upstream equipment was able to mix with the process stream containing chloride and hydrochloric acid was generated, which rapidly corroded the downstream process piping. In consequence, the combustibles leaked a short time after the moisture was introduced.
Park, Gyutae (Institute of Technology Innovation) | Seo, Jinseok (Institute of Technology Innovation) | Abbasi, Majid (Institute of Technology Innovation) | Ro, Yunjo (Institute of Technology Innovation)
Corrosion of overhead system in the distillation unit has been a chronic and unresolved issue even with the injection of neutralizer and corrosion inhibitors. Recently, a light naphtha discharge pump (made of UNS J91150 casing and impeller) malfunctioned, which caused severe damage to the impeller. It was subsequently realized that, prior to the malfunction of the impeller, the pH of the water at the second overhead accumulator unexpectedly dropped to 2.6 with simultaneous increase of Fe concentration. Preliminary analysis of the impeller revealed that it had failed from a combination of corrosion and cavitation. To understand the origin of corrosion, extensive water chemistry analysis was performed, which revealed the presence of corrosive species such as sulfate and nitrate ions, presumably from the flue gas, which would have caused pH to drop. Autoclave corrosion tests also revealed that these species would cause significant corrosion of UNS S41000 which is similar to UNS J91150 used in the pump. In-depth electron microscope study (i.e., SEM, EBSD) on corrosion scale and damaged impeller surface was performed to confirm that the damage mechanism was corrosion-induced cavitation. Details of the analysis will be presented and discussed.
Corrosion in the crude unit overhead is a complex phenomenon that impacts refinery reliability and profitability. It is well known in the refining industry that hydrochloric acid (HCl) is the primary corrosive substance to cause overhead system corrosion. Neutralizer, film-forming inhibitors, and wash water systems are some of the typical industry practices to mitigate acidic attack by condensed water containing HCl. The pH and concentration of chloride ion of the water at overhead accumulator is monitored for corrosion control.1-3 Although most of overhead corrosion is well controlled as expected based on properly designed metallurgy and chemical programs, there are still unresolved corrosion issues.
Recently, the pH of the water at the second overhead accumulator of condensate splitting unit unexpectedly dropped to 2.6, with a simultaneous increase of Fe concentration of up to more than 50 ppm. Several days later, a light naphtha (LSR) discharge pump (made of UNS J91150) malfunctioned. Neutralizer injection into the second stage was immediately applied which recovered the pH and Fe concentrations. Early investigations revealed that the pump was out of order from the severe damage of the impeller, which might be corrosion-related. Field monitoring data showed that the chloride ion concentration of water in second stage accumulator was less than 10 ppm, which is still under the maximum limit. Extensive water chemistry analysis and laboratory autoclave corrosion test was performed to determine unknown substances causing the pH drop of the water and to measure the corrosion rate of various alloys in low pH water. In-depth electron microscope study including scanning electron microscope (SEM) and Electron backscattered diffraction (EBSD) of corrosion scale and impeller metal surface was performed as well to investigate the fundamental damage mechanism of pump impeller.
Hydrazine is used as an oxygen scavenger to control corrosion in steam generating systems, despite being a genotoxic carcinogen. Alternative chemicals, nontoxic corrosion inhibitors or new oxygen scavenger-free water treatment technologies are preferred. A newly developed amine based vapor phase corrosion inhibitor was investigated. Electrochemical tests were conducted and showed a significantly lower corrosion rate in steam generating boilers and boiling water. Short term (720 hours) corrosion tests in boiling water showed a decreased corrosion rate from 5.3 mpy to 1.93 mpy for 50 mg/L VCI and 1.32 mpy (0.001 metal loss per year) for 100 mg/L VCI (Volatile Corrosion Inhibitor) addition. Long term (2,200 hour) corrosion tests in the hot steam generating closed loop system showed a decreased corrosion rate from 8.2-8.9 mpy for the control sample to 0.72-0.74 mpy when washed with 500 mg/L VCI solution. The closed loop system was subsequently maintained at 100 mg/L inhibitor for the test remainder. Inhibitor added at beginning of test resulted in corrosion rate of 1.09-1.24 mpy (with 100 mg/L VCI). XPS (X-Ray Photoelectron Spectroscopy) analysis showed that the amine based inhibitor promoted and stabilized a protective (Fe3O4) magnetite oxide on the pipe internals. This investigation confirmed the inhibitor can be an effective replacement for toxic hydrazine.
The presence of dissolved oxygen in boiler feed water and steam generating systems can present serious problems in a steam generating plant by promoting corrosion and thick scale formation in the feed water system, the boiler and the steam condensate system. Therefore, it is important to remove oxygen from the feed water and also from the condensate where in-leakage can occur. The first step in the elimination of oxygen from the boiler feed water is mechanical deaeration. The second step involves chemical oxygen scavenging to remove the residual oxygen. For many years, sodium sulfite and hydrazine were the preferred chemical oxygen scavengers. However, sodium sulfite contributes solids to the boiler water and hydrazine was found to be extremely toxic.
Oluwabunmi, Kayode (University of North Texas) | Rizvi, Hussain (University of North Texas) | D’Souza, Nandika (University of North Texas) | Nazrazadani, Seifollah (University of North Texas) | Sanders, Steve (University of North Texas) | Hemmati, Vahid (University of North Texas) | Argade, Gaurav (University of North Texas)
The corrosion properties of PBAT/LDH coating on mild steel substrate was investigated. Tafel tests and electrochemical impedance spectroscopy tests (EIS) was used to analyze the corrosion resistance of the coating on the mild steel substrates. The morphological characteristics of the coatings was done using the scanning vibrating electrode technique (SVET) and environmental scanning electron microscopy (ESEM). Buffered saline solution containing NaCl-0.138 M, KCl-0.0027 M at room temperature and pH of 7.4 was used as electrolyte in the 3 corrosion tests. The tafel results showed that least corrosion current density value of 0.315 (μΑ/cm2) was recorded for 50 % LDH concentration in PBAT. This suggests that 50 % LDH in PBAT was about 98.5 % more corrosion efficient than 1018 bare mild steel and 0.7 % more that the 65 % concentration. The EIS results showed a similar trend. The 65 % LDH concentration showed about 25 % greater impedance to current flow over the 50 % LDH concentration in both the nyquist and bode plots. The SVET results revealed that the greatest corrosion protection of the mild steel substrates was observed with 50 % and 65 % LDH coating. This proved that an increased concentration of LDH in PBAT could potentially improve the corrosion resistance of mild steel when in service in a phosphate buffered saline environment.
Metallic materials used in the biomedical field are susceptible to localized corrosion especially pitting when they come in contact with body fluids and other solutions.1 The phenomenon of corrosion, a natural process that all metallic materials irrespective of the service environment suffer from have been examined using different techniques.2,3 Various forms of protective coatings have been used in the past to mitigate this effect.4 The use of organic coatings has recently gained more attention in the medical field as an environmentally friendly and economical technique for the corrosion protection for metals that come in contact regularly with body fluids. Surface coating of many products have to be carried out not only for aesthetic reasons, but specifically to maintain the integrity of the metallic substrate during their service life.5 Poly (butylene adipate-co-terephthalate) (PBAT) an aliphatic-aromatic biodegradable polyester primarily utilized in packaging industry;6,7 was investigated for its potential medical application.8 The non-cytotoxic behavior of the polymer using different cation exchange montmorillonites as filler at less than 10% by weight showed that through cytotoxicity tests, protein absorption analysis and total blood counts, PBAT composites are valuable in biomedical applications.9,10 Though, low hardness values and inherent non-conducting properties makes it suffers rapid delamination when used as a corrosion resistant coating, it was observed that it possessed the ability to enable platelet mobility which improved its mechanical properties with (less than 6%) of layered clay11,12. Based on this, we hypothesized that, reinforcing PBAT with LDH fillers a type of anion exchanged clays also known as hydrotalcite, with a brucite like structure; having a general formula [MII1-xMIIIx(OH)2x]x+(An”)x/n.mH2O, where Mn represents a divalent metal, Mra a trivalent metal, and An- an anion will help to increase the corrosion resistance of PBAT and give birth to a new set of bioinspired coatings suitable for use in medical implants.
The overall objective of the present research is to investigate the effect of operating parameters on the inhibition efficacy of decanethiol in top of the line corrosion (TLC). The effect of water condensation rates, monoethylene glycol (MEG), H2S and hydrocarbon on inhibitor efficacy was evaluated. It was found that the presence of MEG, variation of gas temperatures and water condensation rates did not affect the inhibition efficacy of decanethiol. In sour environments, decanethiol was able to reduce localized corrosion of carbon steel and change the morphology of corrosion products on samples exposed to 30 ppm H2S. In the presence of condensable hydrocarbon (heptane), decanethiol lost its inhibition efficacy and showed very poor persistency. This was due to its low solubility in water.
Top-of-the-line corrosion (TLC) is recognized as one of the most serious concerns encountered in the pipeline transmission of hydrocarbons, where carbon steel is the principal tubular alloy of choice.1TLC occurs in wet gas transportation where temperature gradients between the internal surfaces of the pipeline and the outside environment leads to condensation of water, as well as lighter hydrocarbons from the gas phase. Corrosive gases dissolve into the condensed water formed on the upper surface of the pipe resulting in TLC. Extensive prior research has primarily focused on the use of volatile corrosion inhibitors (VCIs) to mitigate TLC. 2,3,4 The importance and relevance of VCIs are evidenced by the existence of several patents, as well as recent publication of comprehensive reviews thereof.5,6 A few volatile organic compounds have been identified and tested as potential VCIs in the laboratory; their molecules have either filming or neutralizing properties.7,8 The two different classes of volatile corrosion inhibitors examined in this research possessed amine or thiol functionalities. Based on the previously reported results, morpholine and diethylamine show poor inhibition properties; these amines solely increase the pH of the condensed water and do not significantly decrease the corrosion rate.7 In contrast, thiols, especially decanethiol and 11-mercaptoundecanoic acid, show good persistency (in the absence of condensable hydrocarbons), filming behavior and superior mitigation of TLC.8 The good persistency of decanethiol and 11-mercaptoundecanoic acid could be due to their low association by hydrogen bonding and their lower solubility in water.
Although copper is principally resistant to waterside corrosion, conditions can change driving this noble metal to experience corrosion due to chemical composition of water that flows through it c. In some cases of corrosion, the deterioration process may be managed effectively and economically by a number of water treatment alternatives. This paper will explain how copper pipes were corroded at an existing offshore field, and propose ways to mitigate such failures on an offshore field in the future.
In one of the accommodation platforms for ADMA-OPCO, unwanted factors were discovered that led immune copper pipes to corrode heavily when used in water service. In order to predict the corrosivity of the transported potable water, a number of chemical and physical aspects where studied to determine whether potable water was a contributing factor in the corrosion of copper pipes. Potable water, from reverse osmosis on offshore field (a newly commissioned field), is heated in hot water heaters that are installed in the accommodation platform to around 60 °C prior to being distributed to various consumers via the piping network. After a period of one year, pinhole leaks were observed in various locations causing hazardous living conditions for site personnel. In order to investigate the cause of this incident, various lab tests were run to study the chemical composition of potable water before and after getting transported through the copper pipes at different times. Other factors were also studied; this includes the pH and temperature of the transported water.
Analytical report for potable water analysis was carried out measuring the electrical conductivity, such as pH and chloride content. In addition to that, a graphical correlation was represented to justify any relative corrosivity that may have initiated the corrosion process. On the contrary, all results showed that the quality of water being distributed was as per standard and is not related to the deterioration that took place in copper pipes. Finally, a sample of the copper pipe was cut and studied. It was observed that some chloride residues were found in the cut pipe. A thorough investigation was carried out on the quality of water used during the hydro test and that may explaine the reason of chloride residue existance in the pipes present. Therefore, it was tested again to find the chloride content in the sample water used for hydrotest was higher than standard which led to accumulation of chloride in the pipes which was then activated during transport of the tubes that led to the corrosion of highly water corrosion resistant copper pipes.
Since there is no universal water treatment to prevent all corrosion issues in potable waters, a new and more practical way to transport water for domestic use was suggested and currently a feasibility study is being conducted to study the effectiveness of substituting copper pipes with Chlorinated Polyvinyl Chloride (PVC) pipes on offshore platforms. Health aspects, durability and installation cost are being investigated along with the most vital feature which is its ability to operate at high temperatures internally and externally.