Composition Of Corrosion Products Research Articles

Enhanced corrosion resistance of 9Cr alloy steel via Al alloying in simulated harsh marine atmosphere

The corrosion behaviors of Cr9Ni1 and Cr9Ni1Al in simulated harsh marine atmosphere were studied by dry-wet cyclic test (DWCT). Scanning electron microscopy (SEM), energy disperse spectroscopy (EDS) and electron probe microanalyzer (EPMA) were used to observe the cross-section morphology of rust layer. The composition of corrosion products were analyzed through X-ray diffractometer (XRD) and X-Photoelectron spectroscope (XPS). Electrochemical impedance spectroscopy (EIS) was used to determine the electrochemical properties of rusted samples. The results show that the corrosion rate of both 9Cr alloy steels increases continuously during the initial corrosion process of 576 h, which can be understood from α/γ*>1 of the rust layer and the acidification caused by increased CrO3. Interestingly, the addition of 0.7 % Al reduced the corrosion rate of 9Cr steel by more than 26 %. Al not only generates Al2O3 and Al(OH)3 enriched in the whole rust layer, but also optimizes the rust layer in terms of the Cr distribution, composition of Cr-containing compounds, and α-FeOOH content. Importantly, it is proposed that Al alloying weakens acidification through reducing CrO3 content and partial dissolution of the generated Al(OH)3.

Studying the formation of nodules in a Ni-Fe-Cr based superalloy used in fireside corrosion under the impact of creep stress

Creep rupture tests on a Ni-Fe-Cr based superalloy were conducted in a custom-built rig at 750 ℃ under simulated fireside corrosion environment. The impact of creep stress on corrosion was investigated by controlling load level (without loading, loads of 120~195MPa). The phase composition, microstructure, and morphology of surface corrosion products and corrosion-affected area were studied. The mechanism responsible for the production of surface nodules and the observed uniform oxide scale during fireside corrosion are discussed. Results show that the presence of creep stress promotes the development of surface nodules and increases the corrosion-affected area.

Investigations on corrosion behavior of 316LN and 316L austenitic stainless steel under corrosion-deformation interactions

PurposeThis paper aims to explore the influence of corrosion-deformation interactions (CDI) on the corrosion behavior and mechanisms of 316LN under applied tensile stresses.Design/methodology/approachCorrosion of metals would be aggravated by CDI under applied stress. Notably, the presence of nitrogen in 316LN austenitic stainless steel (SS) would enhance the corrosion resistance compared to the nitrogen-absent 316L SS. To clarify the CDI behaviors, electrochemical corrosion experiments were performed on 316LN specimens under different applied stress levels. Complementary analyses, including three-dimensional morphological examinations by KH-7700 digital microscope and scanning electron microscopy coupled with energy dispersive spectroscopy, were conducted to investigate the macroscopic and microscopic corrosion morphology and to characterize the composition of corrosion products within pits. Furthermore, ion chromatography was used to analyze the solution composition variations after immersion corrosion tests of 316LN in a 6 wt.% FeCl3 solution compared to original FeCl3 solution. Electrochemical experiment results revealed the linear decrease in free corrosion potential with increasing applied stress. Electrochemical impedance spectroscopy results indicated that high tensile stress level damaged the integrity of passivation film, as evidenced by the remarkable reduction in electrochemical impedance. Ion chromatography analyses proved the concentrations increase of NO3− and NH4+ ion concentrations in the corrosion media after corrosion tests.FindingsThe enhanced corrosion resistance of 316LN SS is attributable to the presence of nitrogen.Research limitations/implicationsThe scope of this study is confined to the influence of tensile stress on the electrochemical corrosion of 316LN at ambient temperatures; it does not encompass the potential effects of elevated temperatures or compressive stress.Practical implicationsThe resistance to stress electrochemical corrosion in SS may be enhanced through nitrogen alloying.Originality/valueThis paper presents a systematic investigation into the stress electrochemical corrosion of 316LN, marking the inaugural study of its impact on corrosion behaviors and underlying mechanisms.

Enhancing the high-temperature corrosion resistance of HVOF-sprayed NiCoCrAlY coating in marine environment by Pt modification and pre-oxidation

To prolong the service lifetime of hot-section components used in marine environment at elevated temperatures, it is crucial to explore and develop high-temperature corrosion-resistant coatings. High-velocity oxygen fuel (HVOF) sprayed NiCoCrAlY, Pt-modified NiCoCrAlY and pre-oxidized Pt-modified NiCoCrAlY coatings were prepared and investigated. This study is concerned with the performance of three coatings in a simulated marine environment based on the phase composition of corrosion products and microstructure evolution of coating samples combined with first-principles density functional theory. The results show that the NiCoCrAlY coating was subject to accelerated corrosion and extensive aluminum depletion, leading to premature coating failure. The high-temperature corrosion resistance of Pt-modified NiCoCrAlY coating was found to be better than that of NiCoCrAlY coating. In contrast, the pre-oxidized Pt-modified NiCoCrAlY coating offered long-lasting protection and exhibited the best corrosion resistance, which is attributed to the positive synergistic effect between Pt modification and pre-oxidation.

Atmospheric corrosion of carbon steel: Results of one-year exposure in an andean tropical atmosphere in Colombia

In this study was examined the response of carbon steel to atmospheric corrosion after one-year exposure in Valle de Aburrá, a subregion located in northwestern Colombia. The study involved the assessment of material mass loss and corrosion rate, the characterization of atmospheric aggressiveness, and the analysis of the morphology and composition of corrosion products in five different sites. Climatological and meteorological factors were assessed by testing for chloride content, sulfur dioxide levels, and time of wetness (TOW). The analysis of corrosion products was conducted using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. Based on corrosion rates, two sites exhibited a more aggressive environment, with a corrosivity category of C3, while the remaining sites were categorized as C2. The study confirmed the presence of lepidocrocite and goethite phases on the surface of carbon steel at all test sites. Data analysis revealed that both the TOW and the industrial activity significantly influence the corrosion of this metal.

Study on the corrosion behavior of L245 pipeline steel in 100LL aviation gasoline wastewater

The study investigates the corrosion behavior of L245 pipeline steel exposed to 100LL aviation gasoline-contaminated water. The investigation includes analyzing the corrosion rate, morphological changes, and product composition, as well as changes in wastewater ion concentration. Samples of contaminated water were collected and subjected to analytical techniques such as electrochemical testing, morphology characterization, and component analysis. The findings reveal severe corrosion of the specimens, with significant alterations in morphology and product composition. The study reveals that the specimens experienced severe corrosion in the contaminated water environment, with a corrosion rate reaching 0.387 mm/year. Following corrosion, a relatively complete dark green covering layer formed on the specimen surfaces. Moreover, significant alterations in morphology and product composition were observed. Additionally, changes in wastewater ion concentration before and after the reaction were noted. The failure of corrosion of the specimens is due to oxygen uptake and displacement reactions between the iron in the specimens and the Cu2+ in the wastewater, resulting in the dissolution of the basal iron and an increase in the corrosion rate due to the presence of Cu2+.

Evaluation of Corrosion Performance of AZ31 Mg Alloy in Physiological and Highly Corrosive Solutions.

Resorbable Mg and Mg alloys have gained significant interest as promising biomedical materials. However, corrosion of these alloys can lead to premature reduction in their mechanical properties, and therefore their corrosion rate needs to be controlled. The aim of this study is to select an appropriate environment where the effects of coatings on the corrosion rate of the underlying Mg alloy can be discerned and measured in a relatively short time period. The corrosion resistance of uncoated AZ31 alloy in different solutions [Hank's Balanced Salt Solution, 1× phosphate buffered solution (PBS), 4× PBS, 0.9%, 3.5%, and 5 M sodium chloride (NaCl)] was determined by measuring the weight loss over a 2 week period. Upon exposure to physiological solutions, the uncoated AZ31 alloys exhibited a variable weight increase of 0.4 ± 0.4%. 3.5% and 5 M NaCl solutions led to 0.27 and 9.7 mm/year corrosion rates, respectively, where the compositions of corrosion products from AZ31 in all saline solutions were similar. However, the corrosion of the AZ31 alloy when coated by electrochemical oxidation with two phosphate coatings, one containing fluorine (PF) and another containing both fluorine and silica (PFS), showed 0.3 and 0.25 mm/year corrosion rates, respectively. This is more than 30 times lower than that of the uncoated alloy (7.8 mm/year), making them promising candidates for corrosion protection in severe corrosive environments. Cross-sections of the samples showed that the coatings protected the alloy from corrosion by preventing access of saline to the alloy surface, and this was further reinforced by corrosion products from both the alloy and the coatings forming an additional barrier. The information in this paper provides a methodology for evaluating the effects of coatings on the rate of corrosion of magnesium alloys.

Effect of hydrogen on steels in hydrogen sulfide-containing and other environments at gas facilities

The impact of hydrogen sulfide raw materials on steel equipment and pipelines is known and is associated not only with internal corrosion processes, but also with the hydrogenation of carbon and low-alloy steels used. Penetration of hydrogen into steel can lead to the loss of its strength properties and subsequent destruction of gas pipelines operated under high pressure conditions. The manifestations of cracking characteristic of hydrogen sulfide environments, which are a consequence of the penetration of hydrogen into steel, are the most dangerous from the point of view of the safety and reliability of the operation of facilities for the production and transportation of corrosive gas. The effect of H2S on the decrease in ductility of the main types of structural steels was studied based on the results of simulation tests. The formation of blisters (bloatings) and cracks on the surface of steels due to the effect of hydrogen on steel was recorded. The study of the phase composition and properties of corrosion products was carried out in order to assess their possible influence on the processes of steel hydrogenation. The formation of evenly distributed on the surface and the densest corrosion deposits will hinder both the corrosion processes and the penetration of hydrogen into steel. A decrease in the plastic properties of steel is also observed when exposed to hydrogen, which can be transported both separately and together with methane through the main gas pipelines. The main possible means of protecting steels that are unstable to hydrogenation is the use of corrosion inhibitors. It was established that the most effective corrosion inhibitors with rational technologies of application and dosage can protect steels from penetration of hydrogen into them and their destructive effect.

Characteristics of corrosion products of steel bars in modified magnesium oxysulfide cement containing chloride salts

The effects of chlorides on the corrosion of steel bars within a matrix comprising modified magnesium oxysulfide (MMOS) cementitious materials was investigated. The phase composition, morphology and distribution of steel corrosion products (SCPs) were studied. There was basically no corrosion of the steel bars in the MMOS cement without chlorides. A high chloride content and a high water/cement (w/c) ratio in the MMOS matrix had adverse effects on the steel bar corrosion. The primary SCPs in the MMOS mixes were iron oxyhydroxides (FeOOH) and ferric oxide (Fe2O3), while ferrous oxide (FeO) was only observed at low w/c ratios, indicating a lower degree of oxidation. The presence of di-iron nonacarbonyl (Fe2(CO)9) at high w/c ratios suggested a higher degree of oxidation. At lower w/c ratios, rust products readily diffused. Conversely, at higher w/c ratios, these products accumulated close to the steel bars, resulting in a compact structure.

Study on corrosion performance and corrosion product composition of weathering steel and high‐performance steel in simulated C3 environment

AbstractWeathering steel (WS) and high‐performance steel (HPS) have been widely used in bridge engineering. Investigating the corrosion performances of WS and HPS is of great significance to the safety evaluation and maintenance of uncoated WS or HPS bridges, especially aging bridges. This study focused on the correlation between the corrosion performance and composition of the rust layer. Accelerated corrosion tests were conducted on Q345CNH and HPS 70 W to observe their corrosion performance under salt‐spray corrosive environment. Based on the results of corrosion test and the existing corrosion attack evaluation theories, the empirical formulae of uniform corrosion and pitting corrosion were derived. X‐ray diffraction experiments were performed to analyze the composition of the rust layer formed on the surface of steel specimens after various corrosion cycles. The relationship between the composition of the rust layer and the corrosion performance was established. The test corrosive environment was verified to be consistent with the C3 environment. The conclusions of this study could provide guidance for the corrosion evaluation in the following test or practical application.

Degradation behavior of zinc-rich epoxy coatings in simulated marine tidal zone

Degradation behaviors of zinc-rich epoxy coatings (ZRCs) were investigated using a simulated tidal apparatus. The steel substrate can be cathodically protected effectively in both immersion and tidal zones. The tidal level has a remarkable influence on the activation rate of zinc pigments in the ZRCs. Both activation degree and consumption of the zinc pigments in the ZRCs decreases with the rise of tidal level. More durable protection offered by zinc pigments can be achieved at the higher tidal level. The encapsulation of corrosion products hinders the sacrifice of zinc pigments, resulting in the high residual of metallic Zn even after the disability of effective cathodic protection of the ZRCs. Moreover, the tidal level affects the phase composition of corrosion products. In addition to the dominant phases including ZnO and Zn5OH8Cl2, Zn5CO32OH6 and Zn4OH6SO4 are formed in outer layers of the ZRCs at the relatively high tidal level.

Corrosion Behavior of DH36 Steel in the Presence of Acid-Producing Bacterium Citrobacter farmeri

The work aims to provide a basic knowledge of corrosion behavior and corrosion kinetics of ocean engineering steel DH36 induced by Citrobacter farmeri. This study analyzed the corrosion product composition, corrosion morphology, electrochemical information, and weight loss of DH36 in various corrosion systems. The results indicated that with the extension of soaking time, the corrosion products soaked in Citrobacter farmeri suspension were denser than those soaked in artificial seawater. The initial immersion stage led to a higher uniform corrosion rate of DH36 in C. farmeri suspension compared to in artificial seawater, which subsequently decreased over time. DH36 experienced primarily uniform corrosion when immersed in artificial seawater. In contrast, DH36 samples in C. farmeri suspension exhibited significant crevice corrosion, resulting in a maximum pit depth of 5.720 μm. Furthermore, the weight loss of DH36 in artificial seawater and C. farmeri suspension could be described by the power function formula D = 0.0006t0.9579 and D = 0.0007t0.7247, respectively. This study elucidates the fundamental mechanisms through which the presence of C. farmeri induces general and pitting corrosion of DH36 in a marine environment.

Technical Note: Study on Accelerated Corrosion Behavior and Mechanism of X80 Pipeline Steel Welded Joint Under Cyclic Salt Spray Test

The corrosion behavior of X80 pipeline steel double-sided submerged arc welded joints in a marine atmospheric environment was simulated by cyclic salt spray accelerated corrosion test. The corrosion behavior and mechanism of X80 pipeline steel welded joints were studied by means of scanning electron microscopy, x-ray diffraction, and electrochemical test, and the current effect of welded joints was evaluated by means of macroscopic and microscopic morphology, corrosion weight loss, corrosion product composition, polarization curve, and impedance spectrum of samples with different cycles. The results show that with the extension of corrosion time, the corrosion morphology of each region of the welded joint changes from the initial uniform corrosion to a large difference. During the whole process, the surface fluctuation of the base-metal area is small, and no obvious pitting pits are observed. Cracks are gradually generated in the heat-affected zone and the weld metal, and as the cracks expand, the surface pits deepen. The corrosion rate of the three regions of the welded joint showed a trend of rapid increase-slow decrease-slow increase-slow decrease. It provides conditions for further research on the simulation and correlation of accelerated corrosion tests.

Study on corrosion law and characteristics of composite modified basalt fiber concrete in acid environment

The deterioration of concrete materials in the sewage environment is prominent, significantly shortening the structure's service life. Based on the composite modification method, modified basalt fiber high-durability concrete is proposed to solve the problem of insufficient material durability in the sewage environment. The acid environment erosion test was carried out for the modified concrete materials. The macroscopic performance indexes were obtained, such as apparent corrosion characteristics, water absorption rate and compressive strength. The corrosion mechanism and deterioration law of concrete materials under an acid environment were revealed by combining the analysis of the fine structure and corrosion product composition. The results show that the hydration reaction of the modified concrete was adequate. The generation of C–S–H gel and Ca(OH)2 increased significantly. The porosity was reduced by 40%, and the initial strength was increased by 12%. After 240d corrosion, the strength of ordinary concrete was degraded by 41%. The degradation rate of modified concrete was 26%, its residual strength was 1.4 times that of ordinary concrete, and its corrosion-resistant ability was greatly improved. Based on the experiment, the corrosion resistance mechanism analysis was carried out, and it was found that the inorganic aluminium salt compound salt crystal expansion modification effect is better than the sodium methyl silicate reticulated resin film modification. However, after double doping, the corrosion resistance is reduced instead, and it is recommended that inorganic aluminium salts be preferred as anti-corrosion and anti-seepage adding materials. The research results of this paper can better enhance the acid environment erosion resistance of concrete, engineering application prospect is good.

High-cycle fatigue performance of corroded Q690E high strength steel and Q690qENH high-strength weathering steel

High-strength steel and high-strength weathering steel have been increasingly used in engineering constructions. Corrosion leads to a decrease in the fatigue strength of steel, posing a threat to the safety and reliability of the engineering project. The fatigue strength reduction caused by corrosion usually depends on the type of steel and the corrosion time. In this study, indoor acetic salt spray accelerated corrosion test (ASS) and high-cycle fatigue test were carried out on Q690E high-strength steel and Q690qENH high-strength weathering steel, obtaining the time-varying laws of corrosion damage, the composition of corrosion products, and the fatigue life under different corrosion times. The results show that in the corrosion test process, the uniform corrosion depth C and the pitting depth Sz of both types of steel conform to a power function model. In contrast, other pitting parameters conform to a linear model. On the surface of the Q690qENH high-strength weathering steel specimen, α-FeOOH was generated first, which hinders the progress of corrosion. During the fatigue test, under the same stress range, the fatigue life decreases with the increase in corrosion time. For the corroded specimens, the corrosion parameters (C,Sz) were negatively correlated with the fatigue life linearly. This study can provide a reference for the design and use of high-strength and high-strength weathering steel.

Effect of humidity on radiolysis-enhanced corrosion by gamma irradiation on electroless nickel plating

The study reveals that water vapor can cause corrosion of electroless nickel plating under gamma irradiation, even in the absence of dew condensation. To control relative humidity during gamma irradiation, a simple apparatus utilizing saturated salt solutions was developed and validated by cold tests. Irradiation testing of electroless nickel plating was conducted under humidity control at relative humidity of 20%, resulting in surface degradation after 1 MGy total dose. Conversely, no degradation was observed on samples exposed to dry condition with relative humidity of less than 10% after a 5 MGy total dose. Humidity-uncontrolled irradiation tests, where condensation could occur, resulted in more severe corrosion than the humidity-controlled tests. A comparison of the chemical composition of corrosion products between the humidity-controlled and humidity-uncontrolled environments showed nitrate corrosion products were prevalent in the former while hydroxides were dominant in the latter.

Nano-emulsification method as a strategy for oil soluble corrosion inhibitor transform to water soluble

Corrosion inhibitor is one of the most economical and effective approaches to protecting metal pipes in the oil and gas industries. However, a great amount of corrosion inhibitors such as imidazoline, are difficult to distribute fast due to their poor solubility or dispersibility in water, which results in inhomogeneous concentration distribution and ineffectiveness. In this study, nano-emulsification technique was developed to improve the dispersity of mercaptoacetic acid-modified oleic imidazoline (MOI) in corrosive water. The formulation of nanoemulsion is optimized with the phase inversion temperature (PIT) and droplet diameter. The prepared nanoemulsion which the hydrophilic lipophilic balance value (HLB) was 11.5 and the loading of corrosion inhibitor was 20 wt% exhibited remarkable water dispersion performance and its mean particle size was less than 100 nm. Moreover, its dispersion performance in water was significantly better than that of the paraffin oil system, and was similar in the ethanol system. The inhibition performances and mechanisms of nanoemulsion for L245 carbon steel in the H2S/CO2 containing 5.0 wt% NaCl solution were investigated with weight loss measurements and electrochemical tests. In terms of inhibition efficiency, the corrosion inhibitor encapsulated in nanoemulsion was exceeding 90%, which was comparable to the system employing ethanol and liquid paraffin as solvents. Further experimental results indicated that the nanoemulsion system was more consistent with the Freundlich adsorption model, unlike the other two systems which followed the Langmuir adsorption model. The morphology and composition of corrosion products were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) methods. The SEM and XPS results demonstrated that the nanoemulsion system did not change the material type of corrosion products, but had a visible influence on their morphology. In addition, the inhibition mechanism was also revealed by theoretical calculations. These findings suggest that nano-emulsification technique has the potential to improve the solubility or dispersibility of oil soluble corrosion inhibitor, thereby expanding its application fields.

Experimental exploration of metallic chloride salt corrosion of stainless steel sheets

In recent years, biomass generation in China has been steadily increasing. The high-temperature corrosion of the heating surface of biomass boilers is mainly caused by HCl and alkali metal chlorides in the sediment, which seriously affects the efficiency and safety and the degree of economic utilization of biomass energy. In this paper, the corrosion products were characterized by total-immersion experiments under constant temperature on different thicknesses of 304 stainless steel in various concentrations and types of alkali metal chloride salts. Through thermal microscopy scanning and XRD experiments, the composition, characteristics, and microscopic morphology of corrosion products on stainless steel flakes are determined to find out the corrosion mechanism of stainless steel flakes in solution alkali metal chloride salts. The results show that in a water bath at 80 °C, alkali metal chlorides weaken the corrosion resistance of the stainless-steel sheet by destroying the integrity of its reticular structure, thus promoting the chemical reaction between the iron contained in the stainless steel and other elements to generate various types of corrosion products rich in iron. Meanwhile, among various alkali metal chloride salts, the catalytic effect of saturated CaCl2 on the corrosion of 0.1 mm and 0.01 mm stainless steel sheets at 80 °C is the most significant.

Rust expansion cracking behaviour of new Cr alloy-reinforced coral aggregate concrete

The rust expansion cracking behaviour of Cr alloy-reinforced coral aggregate concrete (CAC) was studied by theoretic and experimental methods to analyse the serviceability limit state of concrete. The corrosion product composition of the Cr alloy rebar was analysed to determine the stability and protection of the rust layer. The critical corrosion ratio model of Cr alloy-reinforced concrete was established by considering the influence of water–binder ratio, admixtures and fibres, relative protective layer thickness, Cr alloy reinforcement type and reinforcement placement. The results demonstrated that owing to the loose and porous characteristics of CAC, the corrosion products filled the concrete, resulting in critical corrosion ratio of the rebar being much larger than that of ordinary concrete (OC). When Cr alloy was added to a carbon rebar, the rust layer structure and corrosion products of Cr alloy rebars changed significantly, thereby improving the stability and protection of the rust layer. The protection coefficients of HPB300, Cr1, CrAl, Cr3, Cr5, and Cr8 rebars were 0.211, 0.286, 0.304, 0.490, 0.670, and 0.964, respectively. The rust layer density of the Cr alloy rebar was high, hindering the erosion of the harmful medium in concrete. The critical corrosion ratios of Cr1, CrAl, Cr3, Cr5, and Cr8 reinforcements increased by 0.72%, 1.81%, 4.01%, 11.60%, and 29.35%, respectively. When Cr (5%–8%) was added to the rebar, the corrosion time of reinforcement began to rust and concrete cracking was prolonged. This was beneficial for preventing concrete cracking caused by rebar corrosion.

Failure analysis, corrosion rate prediction, and integrity assessment of J55 downhole tubing in ultra-deep gas and condensate well

Several carbon steel tubing suffered severe corrosion in service which resulted in the leakage of production fluids from tubing string and, consequently, a decrease of well productivity. Optical metallographic microscopy, X-ray diffraction (XRD), combined with weight loss and characterization methods were used to determine the most probable causes of the failure. The results showed that the composition and structure of the tubing joints and couplings were in accordance with the parameter requirements of API 5CT for grade J55. Upon visual inspection, the corroded pipe exhibited significant thickness reduction in multiple locations, which justifies utilizing the triaxial yield of pipe body formula, assuming the minimum measured thickness as the nominal thickness of the pipe. When compared to the upper bound internal pressure requirements in API 5CT, the equivalent stress calculation showed significantly lower failure pressure levels, which provide strong evidence that the pipe could not withstand actual service conditions. The composition of corrosion products was mainly FeCO3 and Fe3O4, and scaling layer were composed of the heavy components of the crude oil, CaCO3 and corrosion products. The scaling layer was protecting the steel surface from corrosion and reducing the corrosion rate. Once the scaling layer was broken, the corrosion rates increased. Also, pitting corrosion rates simulations were conducted at locations with the highest corrosion risk. Results show that at the first 30 days, pitting corrosion rates are the highest at these locations due to many factors including high CO2 partial pressures, acidic pH at these locations, and larger production volumes resulting in an increase of wall shear stresses and higher velocities.