Hastelloy G 35 сorrosion tests for intergranular corrosion resistance

The article is devoted to the analysis of corrosion behavior and assessment of the resistance of Hastelloy G 35. Nickel-based alloys (steels) containing chromium, molybdenum, tungsten, possibly iron are widely used as materials for the manufacture of equipment in high-temperature technological processes using solutions of highly hygroscopic halides (chlorides) in molten halides (chlorides) of alkali metals. During the operation of the equipment, the instability of the surface of apparatus and pipelines to corrosion is determined. In this test, 4 samples of 80×20×3 mm were used, of which 2 samples were subjected to provoking heating, and 2 samples were examined in their normal state. Our tests were carried out in a boiling aqueous solution of iron sulfate and sulfuric acid for 48 ± 0.25 h. Further, the bent samples were examined using an MBS-9 microscope with a magnification of х8. The results of corrosion tests are also presented. As a result of the study, the rate of penetration of corrosion of the alloy was calculated. Hastelloy microstructure is presented. The average depth of destruction was determined from the six maximum values detected in six fields of view. According to the research results, the corresponding conclusions were made.

Corrosion of downhole equipment in hydrogen sulfur-containing environments

Complications associated with the corrosive environment, according to JSC Orenburgneft, NK Rosneft for the period 01.01.2021, are among the prevailing ones at oil and gas production facilities and share the 1st place with the scaling factor - 26% of the complicated mechanized well stock. Downhole equipment failures due to corrosion account for 20% of the total number of fixed failures in 2020. By the type of exposure to a corrosive environment at the fields operated within the perimeter of Rosneft, JSC Orenburgneft, hydrogen sulfide and mixed corrosion (caused by simultaneous action of CO2 and H2S) are predominant. The article presents the calculated data on the physicochemical characteristics of aqueous solutions of H2S. The existing approaches for description of the mechanisms of hydrogen sulfide corrosion of oilfield equipment with examples of corrosive destruction at producing string are described A dynamic matrix of the various protection technologies and their applicability in hydrogen sulfide-containing environments is presented, which is used in the fields operated by PJSC NK Rosneft and filled according to the results of laboratory and pilot field tests. The criterions of attribution of equipment to abnormal fund on basis of classification of factors complicated exploitation and following determination of equipment category being used in localized norms of NK Rosneft are described.

The series of measures for improvement of safety in oil and gas facilities producing, processing and transporting materials containing hydrogen sulfide Part 1. Corrosion-mechanical attack of hydrogen sulfide-containing media on steel equipment. The choice of construction steels and noncorrosive alloys for the oil and gas equipment

The necessity of the complex approach is defined for increase of reliability of the oil and gas equipment operated under pressure of hydrogen sulfide-containing medium, including: - control at the stages of design, manufacturing, commissioning, operation, repair and reconstruction; - organization of corrosion service; - rational choice of materials for equipment manufacturing and its repair; - use of different methods to protect equipment against corrosion: - diagnostics of equipment and evaluation of corrosion protection efficiency; - conducting corrosion tests of materials and corrosion control. The trend of increasing corrosive activity of the products of a number of hydrogen sulfide-bearing oil and gas fields is described. This is associated with their watering and contamination by sulfate-reducing bacteria. All types of corrosion-mechanical damage of steels in accordance with GOST R 53679-2009 (ISO 15156-1:2001) are considered. Comments are given on each of these types of damage and the types of steels that are prone to these defects are shown. The recommendations of GOST R 53679-2009 (ISO 15156-1:2001) are given for the selection of steel equipment operated under pressure of hydrogen sulfide-containing media depending on the type of their corrosionmechanical failure, with comments. Requirements for the use of steels modified with rare-earth metals (REM) and alkaline-earth elements (ALE) intended for operation in hydrogen sulfide-containing media are given.

Results of paint coating full-scale tests for coastal and ship structures in the tropical climate of Vietnam

Full-scale tests are widely used to reliably evaluation the service life of paint and varnish coatings by assessing changes of their protective and decorative properties. Four-year exposure program was carried out in the tropical marine climate in South Vietnam (Dam Bay climate station of the Tre island, Nha Trang) of alkyd, chlorinated rubber coatings on low carbon steel, as well as epoxy coatings of various thicknesses with zinc-rich primer, urethane and acrylic outer layers. The tests were conducted on the base of the existing standards in the field of paints and varnishes intended for coastal and ship structures and were accompanied by the data collection and analysis of the meteorological factors for the classification of the area according to the degree of corrosiveness of the atmosphere. The change in the decorative properties of paint coating was assessed by visual and instrumental methods. The protective efficiency of the coatings was assessed by the time of occurrence of the first local defects or complete destruction of coating layers. According to the results of the conducted field tests, it was found that paint coating combinations correspond to expected lifetime in tropical climate from 2 to 5 years. A typical group suitable for a given climate is a two-component epoxy paint with an acrylic topcoat. A zinc-containing primer is recommended as an anticorrosive undercoat.

Protective properties of superhydrophobic coatings on copper and steel obtained by electrochemical method

Superhydrophobic coatings are obtained by cathodic deposition of copper or nickel on a copper plate with treatment with an ethanol solution of highest carboxylic acids with a long hydrocarbon radical simultaneously or sequentially. They are characterized by a contact angle of water wetting of the order of 155...160°.These coatings protect the copper substrate from corrosion in conditions of 100% humidity for 100...180 days, while maintaining the contact angle within 152…154°. There is no mass loss. The influence of the reversal of the current during electrolysis on the value of the contact angle of wetting is investigated. SEM images of superhydrophobic coatings are presented, indicating multilevel roughness. Superhydrophobic coating on carbon steel is obtained by cathodic deposition of nickel and subsequent surface treatment in an ethanol solution of myristic acid and annealing at 60° for two hours. The influence of the duration of electrolysis on the value of the contact angle of wetting is estimated. Its value is in the range of 151…154°. Exposure of a coated steel plate for 50 days in conditions of 100% humidity is characterized by the absence of weight loss and maintaining the contact angle up to 154°.

Electroplating of iron and its alloys

Analytical review of information on electrodeposition of iron and its alloys from aqueous solutions is carried out. Processes of electroplating of iron and its alloys from aqueous solutions and the principal fields of application of these galvanic coatings are discussed. The principal technological advantages of using iron coatings in the reconditioning of steel parts are considered. Compositions of electrolytes and conditions for plating of iron coatings are provided. Technological parameters of electroplating of iron from industrial electrolytes are considered. Data are presented on the effect of some organic additives on the iron plating process. The effect of the concentration of Fe3+ ions in iron plating electrolytes on electroplating of iron coatings and their physic-mechanical properties is discussed. The data are presented on physic-mechanical properties of iron coatings obtained in different electrolysis modes. Nonsteady-state electrolysis modes are discussed that are used in industry for application of iron coatings. The effect of coating plating conditions on their mechanical properties is studied. Technological parameters of electroplating of iron alloys are considered. Co-deposition of iron with nickel, chromium, titanium, phosphorus, molybdenum, vanadium and tungsten is described. Data are provided on compositions of electrolytes and conditions of electroplating of these alloys. Main fields of application of electroplated iron alloys are discussed. Information is provided.

Local corrosion: calculation in oil field conditions (according to weight measurements)

Complications associated with a corrosive environment, according to Rosneft’s data at 01.01.2020, are among the prevailing at oil and gas production facilities and rank fourth among other factors complicating production – 12% the complicated mechanized wells. Failures due to corrosion are the second largest complicating factors. Based on the results of approbation, the article proposes a method for calculating the maximum rate of local carbon dioxide corrosion, applicable in oilfield conditions, including to complicated stocks of oil wells and pipelines of oil gathering systems. Based on the approbation results, a method for calculating the maximum rate of local carbon dioxide corrosion, applicable in oilfield conditions, including to complicated stocks of oil wells and oil-gathering pipelines systems is proposed in the article. The proposed technique is realizable according to the results one of «traditional» methods the corrosion monitoring - weight (or gravimetric). The approbation results and application possibility of the technique in the pilot tests process in assessing the protective ability of corrosion inhibitors and the selection of the effective dosages in relation to local damages, which are the main cause the oilfield equipment failures according the factor «Corrosive aggressiveness» (one of the complicating factors in terms of gradation, adopted in the Rosneft Company regulations). On practical examples the oilfield equipment operation, the results of corrosion monitoring and the summary statistics the corrosive stock of wells (using the example of an oil Company), the current situation with respect to this type of complication and relevance the issue under consideration is shown.

Electrochemical mechanism of metall corrosion

Corrosion that occurs by an electrochemical mechanism is a combination of cathodic and anodic reactions that occur independently of each other. At that, the metal surface is considered to be equipotential one, i.e. the presence of short-circuited microgalvanic pairs on the surface is not a necessary condition for electrochemical corrosion. The anode and cathode processes are spatially separated. This is provided by the presence of conduction electrons in the interstitial spaces of the metal lattice. The present model of electrochemical corrosion justifies the use of polarization diagrams for the analysis of corrosion processes. The previously proposed model, based on the idea that a necessary condition for electrochemical corrosion is the presence of short-circuited microgalvanic elements on the metal surface, is erroneous. When considering electrochemical corrosion from the positions of this model, the use of polarization diagrams to study corrosion processes is not legitimate.

The study of the effectiveness of corrosion protection of zinc-rich coating on the base of water sodium silicate

The study is examines the assessment of the corrosion-protective properties of zinc-rich coating based on water sodium silicate (ZRC) using the Electrochemical Impedance Spectra (EIS) with AutoLAB PGSTAT204N. The system consists of three electrodes: Ag/AgCl reference electrode in 3 M solution of KCl, auxiliary electrode – Pt (8x8 mm) and working electrodes for determination potential (Ecorr) and impedance measurement, salt spray test method and natural teszzt method at Dam Bay Marine Research Station, Nha Trang, Khanh Hoa, Viet Nam. ZSC can provide good cathodic protection when zinc content is 70% by weight or more. ZSC with a mixing ratio of High Modulus Liquid Sodium Glass / Zinc Powde : 25/75 by weight (working title – TTL-VN) has good corrosion protection after 16 cycles salt spray test and after 18 months natural test in seawater. The paint film has basic parameters as adhesion – 4,41 MPa, flexural strength – 2 mm, pendulum hardness – 0,62 conventional units and initial coating potentia l – 0,96 V Ag/AgCl.

Inhibition of Corrosion of structural steels (St3)

Compositions based on hydroxyethylidene diphosphonic and nitrilotrimethylenephosphonic acids with alkali earth metals (Ca, Mg) are studied as corrosion inhibitors. It is found that the studied compositions are not inferior to their zinc counterparts as regards their corrosion inhibition efficiency and can be used in two-circuit cooling systems.