Stress Corrosion Tests Research Articles

Study on the corrosion and damage behaviours of P110 tubing of deep shale gas wells

This study conducts weight loss corrosion experiments by a high-temperature autoclave to investigate the corrosion behaviours and the damage rules of mechanical properties of P110 tubing under coupling working conditions of multiple factors (temperature 50–155 °C, CO2 content 1%–2%, Cl− content 10,000–20,000 mg/L). It analyses the characteristics of corrosion products of P110 steel using X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy (EDS). In addition, the 3D morphology and size of local corrosion pits are measured microscopically. The mechanical properties’ damage behaviours at different tubing positions are analysed by constant-load tensile stress corrosion tests. The results showed that the average corrosion rate of the tubing reaches the maximum value of 1.627 mm/a at the middle section of the shale gas well. With an increase in temperature and CO2 partial pressure, the depth of the local corrosion pits on the tubing rises from 3.8 to 25.0 μm. The yield strength and tensile strength of the tubing at the bottom-hole section reduced by less than 8%, and the coupling damage effect of stress and corrosive mediums is serious. The tubing shows a sensitivity to stress corrosion cracking at the bottom-hole section. It was recommended that corrosion inhibitors should be cyclically added to inhibit CO2 corrosion to control the corrosion rate of the tubing within the range of medium-degree corrosion, thus ensuring that the strength reduction of P110 tubing under the corrosion working conditions containing CO2 and sulphate-reducing bacteria coupled with tensile stress is within the controllable range of safety factor.

Effect of interrupted aging on mechanical properties and corrosion resistance of 7A75 aluminum alloy

The effects of interrupted aging on mechanical properties and corrosion resistance of 7A75 aluminum alloy extruded bar were investigated through various analyses, including electrical conductivity, mechanical properties, local corrosion properties, and slow strain rate tensile stress corrosion tests. Microstructure characterization techniques such as metallographic microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were also employed. The results indicate that the tensile strength of the alloy produced by T6I6 aging is similar to that produced by T6I4 aging, and it even exceeds 700 MPa. Furthermore, the yield strength increases by 52.7 MPa, reaching 654.8 MPa after T6I6 aging treatment. The maximum depths of intergranular corrosion (IGC) and exfoliation corrosion (EXCO) decrease from 116.3 and 468.5 µm to 89.5 and 324.3 µm, respectively. The stress corrosion factor also decreases from 2.1% to 1.6%. These findings suggest that the alloy treated with T6I6 aging exhibits both high strength and excellent stress corrosion cracking resistance. Similarly, when the alloy is treated with T6I4, T6I6 and T6I7 aging, the sizes of grain boundary precipitates (GBPs) are found to be 5.2, 18.4, and 32.8 nm, respectively. The sizes of matrix precipitates are 4.8, 5.7 and 15.7 nm, respectively. The atomic fractions of Zn in GBPs are 9.92 at.%, 8.23 at.% and 6.87 at.%, respectively, while the atomic fractions of Mg are 12.66 at.%, 8.43 at.% and 7.00 at.%, respectively. Additionally, the atomic fractions of Cu are 1.83 at.%, 2.47 at.% and 3.41 at.%, respectively.

Mechanism of corrosion behavior induced by precipitates under plastic compressive stress in Mg-Gd-Y alloys

Through independently developed stress-loading equipment, stress corrosion tests on Mg-Gd-Y alloy were conducted in a 3.5 wt% NaCl solution. The effects of plastic compressive stress on the corrosion behavior of the alloy were thoroughly investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) among other microscopic analysis techniques. The results indicate that the alloy mainly consists of α-Mg grains, Mg24Y5 phase, Mg5Gd phase, and LPSO phase. The corrosion behavior of the Mg-Gd-Y alloy is significantly influenced by the microstructure of the interface between the precipitates and the matrix, the potential difference, and the stress state. In the unstressed state, the Mg24Y5 phase first induces corrosion at the edges of the α-Mg grain boundaries, which then spreads internally. Upon the application of plastic stress, the corrosion-inducing capability of the LPSO phase on α-Mg grains notably increases. This discovery provides new insights into the mechanisms by which plastic compressive stress affects the corrosion behavior of Mg-Gd-Y alloys and offers an important basis for the theoretical research and anti-corrosion design in the engineering applications of this alloy.

Stress corrosion tests for prestressing steels—Part 1: The influence of surface condition and test solution composition on hydrogen charging

AbstractTests for assessing prestressing steels' susceptibility to hydrogen‐induced stress corrosion cracking are essential for approvals, in‐house monitoring, and third‐party material testing. According to ISO 15630‐3, the time to brittle fracture by constant load under corrosive conditions in thiocyanate test solutions (A or B) at 50°C is measured. In the literature, a high scattering in stress corrosion tests is reported, which questions the integrity of the test procedure. This paper shows the results of studies about the influence of solution composition on hydrogen charging in electrochemical and permeation measurements. Electrochemical experiments show that polished steel surfaces without common drawing layers have more consistent free corrosion currents, polarization resistances, and B‐values in solution A with low scattering compared to the solution B experiments. The influence of temperature at 50°C and an ambient temperature of 22°C was also tested.

Investigation into hydrogen induced fracture of cable bolts under deep stress corrosion coupling conditions

The coupling effects of geostress and multi-attribute corrosion environments are the major causes of damage and rupture of prestressed cable bolts in deep underground environments. To determine impacts of different environmental factors on stress corrosion cracking of cable bolts in underground conditions, the accelerated stress corrosion tests and finite element numerical simulations were carried out. By implementing the material diffusion theory and appreciating the hydrogen induced lattice expansion effects, the diffusion and aggregation behavior of hydrogen in cable bolts were simulated. The influences of stress intensity and hydrogen concentration on failure mechanisms of cable bolts were studied by considering the hydrogen induced expansion strain. The failure only occurred in the environments where sufficient hydrogen concentration existed. The hydrogen diffusion flux and distribution were consistent with stress concentration distribution. The prestress accelerated the hydrogen diffusion to stress concentrated position leading to a greater strain in the stressed areas, which consequently induced hydrogen expansion stress and decreased cohesion strength of lattice near crack tip. The fractographic features of failed specimen were analysed and hydrogen assisted fracture was confirmed to be one of the main failure mechanisms leading to stress corrosion failures. The methodologies proposed could be used to study the diffusion and distribution of hydrogen in metals and the obtained results improved the understanding failure mechanism of hydrogen assisted SCC.

Experimental and numerical study on the degradation law of mechanical properties of stress-corrosion steel wire for bridge cables

In this paper, the stress corrosion and monotonic tensile test of corroded steel wire were carried out. The effects of different corrosion ages and stress levels on failure modes, stress-strain curve and mechanical properties of corroded steel wire were discussed. Then, a finite element model of steel wire considering real surface morphology was established, and the surface stress distribution and the failure of steel wire under different corrosion degrees were compared. The relationship between stress triaxiality and critical equivalent plastic strain to different corrosion parameters was given. Finally, the degradation model of mechanical properties of corroded steel wires was established. The results showed that the failure patterns of steel wires with different degrees of corrosion were mainly divided into three types: cup cone shape, milling cutter shape and splitting shape. The shear lip zone of fracture section basically disappeared with the increase of stress corrosion, and the location of fiber area was transferred from the inside to the surface of steel wire. The decrease in strength and elastic modulus of the specimen under stress corrosion was four times and three times greater than that under non-stress corrosion, respectively. In addition, the crack position of specimen changed from the inside of section to the location of corrosion pit with the increase of corrosion degree. The fracture equivalent plastic strain decreased gradually, while the stress triaxiality increased. When the degree of corrosion reached 19.53%, the fracture equivalent plastic strain decreased by 55.41% from 0.314 to 0.140, and the stress triaxiality increased by 23.53% from 0.390 to 0.510. The influence of uniform thickness loss on the stress triaxiality was less than that of pit depth-width ratio. The larger the depth-width ratio, the larger the maximum stress triaxiality corresponding to the failure element. The constitutive model proposed in this paper could reflect the degradation law of mechanical properties of corroded steel wires.

Simultaneous enhance of the thermal shock resistance and slag-penetration resistance for tundish flow-control refractories: The role of microporous magnesia

As the low thermal shock and slag-penetration resistance of the magnesia castables cause the premature failure of tundish flow-control devices leading to the pollution of steel, the microporous magnesia with high closed porosity and intergranular CaZrO3 phase was utilized for simultaneously enhancing the high-temperature performance. The thermomechanical stress and slag corrosion tests indicated that since the micro-closed pores effectively relieved the thermal stress and CaZrO3 absorbed massive crack-propagation energy, the cold modulus of rupture and residual strength ratio respectively reached 14.4 MPa and 73.4% after thermal shock cycles, nearly half higher than that of the fused magnesia based castables. Meanwhile, the synergistic effect of micro-closed pores and intergranular CaZrO3 phase significantly reduced the slag-wettability, improved the interfacial energy and dihedral angle, leading to the decline of slag penetration indice (decreased by ∼34.8%). This study suggests a potential approach to generate new magnesia based castables in tundish for making clean steel.

Effect of stress loading on hot salt corrosion behavior of TiAlTaN/CrAlN multilayer coatings

The hot salt corrosion behavior of TiAlTaN coating and TiAlTaN/CrAlN multilayer coatings with different modulation periods under external stress condition were studied. The complex stress distribution on the specimen surface was obtained by designing a double-sided notched tensile specimen, and then the hot salt stress corrosion test was carried out at 500 °C for 120 h. The TiAlTaN monolayer coating had obvious stress cracking under stress loading, while the TiAlTaN/CrAlN multilayer coatings showed good resistance to hot salt stress corrosion crack even under high stress. The performance improvement was attributed to the role of multilayer interfaces in inhibiting microcrack growth and diffusion of the corrosion medium into the coating. In particular, the TiAlTaN/CrAlN-10 multilayer coating with smaller modulation period not only had better hot salt corrosion resistance, but also showed excellent resistance to crack propagation under stress loading, forming effective protection for the titanium alloy substrate.

Research on the Development, Testing, and Evaluation of the Dual-Opening Anti-Blowout Oil Draining Device

During the tripping of the sucker rods and tubing from the wells with sucker rod pumps (SRP) in Tarim Oilfield, there are multiple challenges encountered, such as heavy oil, deep pumping, substantial load differences, and corrosive gas like H2S, etc., making the traditional anti-blowout oil draining device inefficient for operational needs and environmental requirements during pumping and intervention of the producing wells. In order to resolve such problems, Tarim Oilfield has developed a novel anti-blowout oil draining device with dual-opening function of rupturing + impacting by referring to the structure of high-pressure rupturing oil draining device with high opening success rate and conducting structure analysis, strength checks, and flow capacity calculations of the oil draining valves. The novel anti-blowout oil draining devices have passed a series of mechanical tests, corrosion resistance tests, and functional tests, such as indoor constant tensile stress-corrosion test, tensile strength test, collapse strength test, HIC test, electrochemical corrosion test, and tests of tool opening and closing, making up and breaking out, etc. The theoretical calculation and test show that the novel dual-opening anti-blowout oil draining device can not only meet the requirements of deep pumping, high gas-liquid ratio, substantial loading differences, and H2S corrosion resistance, but also be used in highly deviated wells, horizontal wells, and heavy oil producers. To conclude, the novel anti-blowout oil draining device will not pose any impacts on pump colliding operations. Moreover, the pump colliding operation can be used to eliminate the gelled debris attached to the pump valve and ball seat while ensuring anti-blowout oil drainage, returning the producer back to normal production.

Effect of Normalizing on Impact and Corrosion Resistance of Low-temperature Service Seamless Steel Pipe

The seamless line pipe, which has fine low temperature impact properties for Low-temperature Service and good H2S corrosion resistance, was investigated through chemical composition designing, optimizing smelting-rolling processes, and heat treatment processes following ASTM A333 standard. The influence of normalizing on the impact property and corrosion resistance was studied by optical microscope, scanning electron microscope, transmission electron microscope, mechanical test and corrosion test. It is demonstrated that the low temperature mechanical properties and anti-H2S corrosion properties of hot-rolled trial-pipe and normalized trial-pipe meet ASTM A333 standard. The microstructure of hot-rolled trial-pipe is pearlite and ferrite, and the grain distribution is uniform and grain size is fine. The dominated precipitates phase are TiN particles in hot-rolled trial-pipe. Ductile to brittle transition temperature is determined at -60 °C. The grain refinement is achieved after normalized and the main precipitates are TiN particles together with a few VN particles. Ductile tobrittle transition temperature was further lowered, at - 80 °C. The corrosion behavior of the material was examined by hydrogen induced cracking (HIC) corrosion test, sulfide stress corrosion (SSC) test and polarization test at various polarization scanning rates. It is observed that the anti-HIC corrosion performance and SSC corrosion resistance are similar for both hot-rolled and normalized pipes, but the performance of electrochemical corrosion of normalized pipe is better than hot-rolled pipe, which indicates that the normalized pipe is more suitable for demanding corrosive environments.

Effect of Strain Levels on the Corrosion Resistance of an Enamel-Coated Steel Rebar

The effect of strain levels on the corrosion resistance of an enamel-coated steel rebar is experimentally investigated in this study. Enamel coating was applied on the surface of a steel rebar by using the wet process. A strain gauge was attached on the surface of the coated steel rebar to record the strain levels and a plastic container was mounted for electrochemical corrosion tests. A stress-corrosion test set-up was designed to conduct corrosion and tensile tests simultaneously. The strain levels considered include 0 µε, 300 µε, 600 µε, 900 µε and 1200 µε, and the electrochemical techniques employed include open circuit potential, linear polarization resistance and electrochemical impedance spectroscopy. The microstructure of the enamel coating was also examined with scanning electron microscopy. Results show that the enamel coating has a thickness of ~150 µm, and there are some air bubbles in the coating. The average corrosion current density of the uncoated steel rebar decreases from 18.64 µA/cm2 to 14.39 µA/cm2 in NaCl solution due to the generation of corrosion products. The corrosion current density of the enamel-coated steel rebar gradually increases from 0.49 µA/cm2 when the strain is zero to 0.65 µA/cm2 as strain reaches 1200 µε, which is almost 40 times lower than that of the uncoated steel rebar. Impedance spectrum results show that the corrosion resistance of enamel coating decreases with an increase in the tensile strain level; however, it still protects steel rebar from corrosion to some degree.

Controlling the size of GO in GO/nAg nanocomposite coatings on orthodontic nickel-titanium alloy toward excellent anti-corrosion, antibacterial, and tribological properties.

High surface friction and lack of antibacterial properties limit the efficiency of fixed metallic orthodontic appliances. Graphene oxide/silver (GO/nAg) nanocomposite coatings were constructed on the surface of a representative nickel-titanium (NiTi) alloy using different sizes of GO via pulse electrodeposition; these coatings were characterized in terms of their microstructure, surface properties, and related biological features. Small-sized GO (SGO) with a lateral size of about 70 nm had more sites for nAg to bind, which helped to form serried and uniformly dispersed nAg; this decreased the coefficient of friction to 0.1, reduced the corrosion current density by ten times, and decreased the amount of corrosive ions, as determined from electrochemical and stress corrosion tests. In the coating containing large-sized GO (LGO), the prolonged growth of nAg resulted in a larger size and scattered distribution, thus having limited optimization in terms of friction and corrosion resistance. Both GO/nAg coatings were biocompatible with L929 cells and adhesion to human gingival fibroblast cells. The LGO/nAg coating released two folds of Ag+ than the SGO/nAg coating initially, while the latter exerted a stable antibacterial effect over seven days against 90% Streptococcus mutans through sustained release. It is suggested that the size of GO could regulate the mechanical and biological properties of GO/nAg coatings. This study aims to improve the efficiency of orthodontic treatment and promote the clinical popularization of multifunctional GO/nAg nanocomposite coatings in the oral environment.

Analysis on the fitness of heat-resistant steel as casing material in corrosive environment at high temperature

This study investigates the performance of heat-resistant steel in a corrosive environment at high temperatures, focusing on mechanical characteristics and corrosion behavior. Firstly, the performance of heat-resistant steel at high temperature was verified using mechanical property measurement, fracture failure analysis, and high-temperature creep test. The results indicate that the tensile strength and yield strength of heat-resistant steel at 350 °C are separately for 930 MPa and 776 MPa. The specimen has good creep resistance and no creep between 100 ∼ 350 °C. After establishing that the high-temperature performance of heat-resistant steel complies with the specifications, the weight loss and stress corrosion tests were carried out in a corrosive environment at high temperatures. The results reveal that the corrosion rate is 0.9504 mm/a at 350 °C, and the corrosion products mainly consist of FeSx, FeCO3 and Fe3O4. The four-point bending test specimen did not crack at all test temperatures. The results show that heat-resistant steel has excellent properties and can be used as the casing material of a complex deep well at high temperatures.

Localized Environment Enriched with Hydrogen Sulfide for Inducing Sulfide Stress Cracking on Type-430 Stainless Steel

Exposure tests to hydrogen sulfide environments are frequently used to evaluate hydrogen sulfide stress corrosion cracking (SSC) in steel. However, there are many safety restrictions in handling hydrogen sulfide, and the maintenance of the facilities is very costly. To improve this situation, an electrochemical measurement method that can be used even in laboratories to simulate hydrogen sulfide stress corrosion tests easily. Specifically, a safe hydrogen sulfide corrosion test method was developed using a local hydrogen sulfide concentration environment near the steel surface.A local acidic environment of pH 3-4 was induced by constant potential anodic polarization of a platinum electrode below 2 VSHE in an aqueous sodium sulfide solution. Exposure of the carbon steel surface to a local acidic environment resulted in the formation of iron sulfides such as FeS and FeS2 on the surface, accompanied by a negative shift of the carbon steel electrode potential and an increase in the microelectrode current. Local acidification of a potentiostatically polarized type-430 steel surface confirmed the existence of a critical potential at which the steel surface begins to depassivate and actively dissolve. It was suggested that the substitution of iron oxide for iron sulfide in a hydrogen sulfide environment determines the sulfidation of the steel surface. Using this method, furthermore, the formation of cracks was successfully induced on the surface of type-430 steel under tensile stress loading.

A comprehensive assessment of the galvanic corrosion behavior of an electrically assisted pressure joint of dissimilar stainless steel alloys under uniaxial tensile stress

The effect of uniaxial tensile stress on the galvanic corrosion behavior of a dissimilar joint of stainless steel alloys is investigated in 0.5 M Na2SO4 electrolyte solution at room temperature. The experimental stress-corrosion test results reveal that the application of uniaxial tensile stress causes a decrease in the corrosion potential and an increase in the corrosion rate compared to the nonstressed specimen. A numerical model is established and validated using the results from the experimental stress-corrosion tests. Consequently, a series of case studies is presented to investigate the galvanic corrosion behavior of the joint under some applied tensile strains.

Improving stress corrosion cracking resistance of AZ31 magnesium alloy in Hanks’ solution via phosphate conversion with laser shock peening pretreatment

The present work aims to improve stress corrosion cracking (SCC) behavior of AZ31 magnesium alloy in Hanks’ solution via laser shock peening (LSP) and subsequent phosphate conversion (PC). The surface and cross section morphology, microstructure and scratch behavior of coated samples were characterized with and without LSP pretreatment. Additionally, immersion, electrochemical corrosion and stress corrosion tests in Hanks’ solution were conducted to evaluate the suitability of LSP and PC composite processing for improving corrosion resistance and the stress corrosion susceptibility of AZ31 magnesium alloy in Hanks’ solution. The experimental results showed that the grain refinement and high specific area generated by LSP promoted the deposition of coating and then improved the scratch resistance of coating. The LSP/PC composite coating significantly enhanced the corrosion resistance and mechanical properties of AZ31 magnesium alloy in Hanks’ solution, which was attributed to the dense coating formed by PC reaction and the strain strengthened layer induced by LSP pretreatment on the sub-surface of the material.

Study on Stress Corrosion Properties of 1Cr17Ni2 Stainless Steel

1Cr17Ni2 stainless steel is used in aviation, ships, machinery, and other fields. However, stress corrosion will lead to its strength reduction, thus failure. In this paper, we studied the stress corrosion resistance of 1Cr17Ni2 stainless steel bolts and nuts using fasteners’ stress corrosion test method and fasteners’ stress corrosion test method in a simulated environment with the accelerated stress corrosion test method of fasteners. The influence of seawater concentration, temperature, stress, test duration, and other parameters was fully considered during the test. The test results showed that 1Cr17Ni2 stainless steel would appear to stress corrosion crack under a specific corrosive environment, but the occurrence probability was not high. Therefore, in the complex seawater salt fog environment, the stress corrosion of 1Cr17Ni2 stainless steel cannot be ignored, which provides a practical reference for applying 1Cr17Ni2 stainless steel in a complex environment.

Effect of Cl− and rust layer on stress corrosion cracking behavior of X100 steel base metal and heat-affected zone in marine alternating wet/dry environment

The influence of stress corrosion cracking (SCC) behavior of ×100 steel base metal (BM) and heat-affected zone (HAZ) with a rust layer under an alternating wet/dry condition was investigated. The results indicated that ×100 steel was highly susceptibility to SCC, especially the HAZ. When the concentration of Cl − exceeded 2 mol/L, the magnitude of the SCC susceptibility of ×100 steel increase was less. The corrosion product layer had an effect on electrochemical corrosion and SCC. Cl − deposited in the corrosion product layer can cause pitting, and an increase in local H − owing to acidification, this outcome might lead to an increase in SCC susceptibility. The SCC of ×100 steel involved the mechanism of anodic dissolution (AD) and hydrogen evolution (HE). • The SCC behavior of ×100 steel BM and HAZ were studied by a self-made alternating dry/wet stress corrosion test device. • The effect of high concentration Cl − on the SCC susceptibility of ×100 steel was systematically studied. • The composition of the rust layer and its effect on SCC behavior are clarified. • Comparative analysis of SCC mechanism of BM and HAZ under high Cl − concentration.

Stress corrosion studies of AL 2014 alloy using synthesized pyrimidin derivative inhibitor in different concentration of HCl solution

The stress corrosion resistance of AL 2014 in high temperature acidic media usingthe inhibitors MPPA and AMPO has been evaluated using an autoclave. The liquid melt metallurgy technique using vortex method was used to fabricate AL 2014 alloy. Stress corrosion tests were conducted using weight loss method for different exposure time, normality and temperature of the acidic medium. The corrosion rates of AL 2014 alloy was lower to that of Concentration increases of the inhibitor.

Microstructure and properties of intercritically reheated coarse-grained heat affected zone in pipeline steel after secondary thermal cycle

As a kind of high strength microalloyed steel, pipeline steel has high strength and toughness. However, the formation of the intercritically reheated coarse-grained heat affected zone (ICCGHAZ) during the welding process is an important limitation affecting its performance. Herein, microstructural transformation in the ICCGHAZ of X100 pipeline steel after a secondary thermal cycle and hydrogen sulfide stress corrosion cracking (SSCC) resistance of the transformed microstructure are investigated. The microstructure of X100 pipeline steel after the secondary thermal cycle is similar to that after the primary thermal cycle, comprising lath bainite and granular bainite. With an increase in t8/5 (time required for the material to cool from 800 °C to 500 °C), the M-A constituents that continuously precipitate along the prior austenite grain boundaries in the second thermal cycle are coarsened and form a necklace-type structure. A variation in t8/5 does not significantly affect the crystallographic characteristics of the ICCGHAZ. The stress corrosion test shows that the resistance to SSCC decreases and cleavage fracture characteristics become more noticeable with an increase in t8/5.