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The corrosion behavior of metal materials in soil environments has been intensively studied recently. Even so, the detailed corrosion mechanisms remain elusive, especially regarding the role of metal ions. In this study, we investigated the effect of ion diffusion on the corrosion processes of carbon steel via scanning electron microscopy (SEM), in...
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Context 1
... measurement of weight loss of the carbon steel in three different media is shown in Fig. 3. The weight loss in solution increased with increasing experimental time. For the fresh surface of the sample in the early stage, the surface metal continuously dissolved into the simulated solution; however, the early corrosion products provided a protective effect in suppressing the corrosion process formed on the surface, and thus ...
Context 2
... with Fig. 3, we further concluded that the diffusion rate of ions was fast, and therefore, rust could not accumulate on the matrix. Although rust was formed, the structure was still very loose and its protection ability was very poor. For the comparison between agar gel colloid and kaolin, the inection point of the weight loss curve of kaolin was ...
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This paper describes a systematic study into the initiation and propagation of filiform corrosion (FFC) on industrially important Zinc-Aluminium-Magnesium (ZAM) alloy coatings for steels. An artificial scribe defect is created in model organic coatings applied to ZAM. Corrosion is initiated using HCl, NaCl, FeCl2 and acetic acid. Only acetic acid i...
Citations
... The formation of a stable rust layer from enriched alloy elements [1] results in a higher atmospheric corrosion resistance of weathering steel compared to other steels [2]. In a marine atmosphere, a rust layer can effectively isolate the steel substrate from corrosive media such as O 2 , H 2 O, and NaCl particles [3][4][5]. The most common method for increasing the content of alloying elements in the rust layer is to directly add Cu, Cr, Ni, and P to steel during the smelting process [6,7]. ...
The corrosion mechanism of the low carbon low alloy steel with Al2O3 particles and rare earth (RE) oxide particles was compared in a simulated marine environment. It is shown that when the Al2O3-containing particles are introduced, the number density of nonmetallic particles of the steel increases twice, and the average particle size decreases from approximately 2.4 μm to 1.4 μm. With the introduction of Al2O3-containing particles, the amount of pitting corrosion increases. Furthermore, pitting corrosion occurs more uniformly owing to the fineness of the Al2O3 particles, thereby leading to smaller, shallower pits after the Al2O3 particles are shed. Hence, the corrosion performance of the steel with Al2O3 particles is significantly improved than that of the steel without Al2O3 particles. By adding RE oxide particles into steel, the nonmetallic particles in steel are refined but not as effectively as that achieved by adding the Al2O3-containing particles. Different from Al2O3 particles, Cu is obviously enriched in the location of RE oxide particles at the initial corrosion stage, which makes the steel exhibit the best corrosion resistance. Cu enrichment is attributed to the mobile Cu present in the rust layer and to the micro acid region formed around the RE oxide particles.
... However, the early corrosion products provided a protective effect in suppressing the corrosion process formed on the surface. Thus, the CR slowed gradually with the formation of a rust layer [25]. Figure 5 shows a log-log plot of the penetration depth (ρ, µm) and the time of exposure (t, years) using the following equation [26]: ...
The corrosion behavior of carbon steel X36 (CSX36) in solutions of soils collected from different areas linked to the main pipe network of a water distribution system in Jeddah City (Obhour Al Shamaliyah, Ob-Sh; Al Shateie, Sh; Al Safa, Sf; Al Samer, Sa; and Al Jameaah, Ja) at an ambient temperature (23 ± 1 °C) was studied. The corrosion behavior was monitored using various techniques, such as weight loss and electrochemical (open circuit potential [OCP]; electrochemical impedance spectroscopy; and potentiodynamic polarization) measurements. Visual and microscopic examinations of the surface morphology of the studied metals were evaluated and discussed. The corrosion rates in all the studied soil solutions decreased with an increase in the immersion period over 80 weeks. The corrosivity of the studied soils based on weight loss measurements followed the order Sh > Ja > Ob-Sh > Sa > Sf. The value of the OCP gradually shifted to more negative values, indicating a higher tendency to corrode. For the soil solutions studied, the Ecorr shifted to more negative values, indicating that the corrosion process was under cathodic control. The values of icorr and 1/Rp tended to increase as the soil resistivity decreased. Moreover, there was good consistency between the corrosivity order of the studied soil solution obtained from electrochemical impedance spectroscopy and PDP measurements in the following order: Ob-Sh > Sh > Ja > Sa > Sf. A comprehensive assessment of the soil corrosivity based on various soil variables revealed that soil solutions of Ob-Sh and Sh are extremely corrosive, while the rest of the soil solutions are noncorrosive.
... The steel corrosion process consists of two basic reactions which take place in different components of microstructure: the anodic reaction of iron (Equation 7) and the cathodic reaction for metals and alloys in aerated near neutral pH solutions, which consist in the oxygen reduction (Equation 8) [76]. ...
The corrosion behavior of ferrite-martensite and ferrite-bainite dual-phase steels in NaCl, CaCl2, and MgCl2
solutions was studied by cyclic potentiodynamic polarization (CPP) and electrochemical noise (EN) techniques.
The results showed a trend for mixed corrosion due to no passivation by a protective oxide layer. For the ferritemartensite
dual-phase steels, the ferrite phase was preferentially corroded compared with the martensite phase in
test solutions. Bainite-microstructure in ferrite-bainite dual-phase steels was preferentially corroded compared
with ferrite-phase in CaCl2 and MgCl2 solutions. The corrosion behavior in test solutions in dual-phase steels
could be divided into three steps: dissolution in anodic-phase/microstructure, non-uniform corrosion, and
localized corrosion. The results indicated that factors such as galvanic coupling between ferrite/martensite,
ferrite/bainite, metallic-matrix/inclusion-phases, metallic-matrix/secondary phases, and self-corrosion of each
phase and microstructure contributed to the non-uniform and localized corrosion in dual-phase steels.
... As a result, the direct contact between the steel surface and the erosive soil environment is regarded as a signicant cause of its corrosion failure. 9,13 Previously, extensive research efforts have been devoted to the study on the electrochemical corrosion reaction at the soil-steel interface, [14][15][16][17] and a more mature theory has been established. Most of the reactions correspond to oxygen-depolarized corrosion. ...
... They were assigned to FeOOH, Fe 2 O 3 , and Fe 3 O 4 , respectively. 16,42 It can be seen that the content of corrosion deposits decreases with the lowering soil temperature. At temperatures above freezing point, the Fe 2 O 3 content is higher. ...
... When the dissolution of the iron anode occurred, and Fe 2+ was formed, the difference of concentration gradient was generated, leading to gradual diffusion. 16 The soil electrolyte has a larger inherent heterogeneity; therefore, the vast majority of iron ions continued to undergo reactions to form iron oxides or oxy-hydroxide compounds attached to the steel surface, and its small fraction diffused to the pores of the soil. ...
In this study, X80 pipeline steel was embedded in silty soil with different salinities and subjected to corrosion at a constant temperature for 24 h before electrochemical testing. The effect of soil medium, temperature, and salt content on the kinetics of corrosion behavior of X80 steel was analyzed. Furthermore, the compositions and structures of the corrosion products were analyzed by X-ray photoelectron spectroscopy and scanning electron microscopy. Based on the results, the anodic dissolution reaction mechanism of X80 steel in silty soil was determined, the differences in the corrosion process caused by different soil systems were comprehensively contrasted, and the impact of the migration process of heterogeneous silty soil on corrosion behavior under different conditions was systematically explored. Comparative analysis revealed that chloride ions possess strong adsorption ability at temperatures above freezing point and that more oxidized substances are present in the deposited layer on the surface of corroded steel, which facilitates the occurrence of corrosion under deposition. At temperatures below freezing point, the sulfate ions present in the pore solution contribute to crystallization-induced expansion and lead to swelling and deformation of the soil, rendering the X80 steel more prone to corrosion in sulfate corrosion environments.
... layer on the surface of the external X70 pipeline. In this case, the electrochemical reaction of iron ions, Fe 2+ was released from the anodic area to the cathodic zone, hydrogen ion, H + (acidic soil) from the soil that infiltrates into soil cavities is the primary ele- Table 3 Elemental composition of corrosion products for in-situ exposure marked in Fig. 2 ment that causes corrosion in in-situ conditions [21][22][23]. The presence of moisture, which functions as an electrolyte, also plays a crucial role. ...
The corrosion of underground pipelines, especially on external surfaces, is generally influenced by soil properties and surrounding environmental conditions. Corrosion of the external oil and gas pipeline could result in a catastrophic incident in the oil refinery sectors due to friable points and corrosion prevention failure, restricting pipeline performance under high-pressure situations. Furthermore, this issue could cause substantial financial costs for the industry, notably in pipeline maintenance. In this study, an investigation was done focusing on the surface morphology change of this external pipeline under a series of exposure times (14, 30 and 60 days) at ambient and acidic peat environments. Organic peat with a pH range of 4.5–5.5 was chosen, as it can potentially induce surface deterioration on this pipeline external surface. SEM images revealed the production of dispersive corroded deposits form and tiny irregular porosity on the surface of X70 steel, while EDX proved the presence of Fe, O, and C elements associated with corrosion products. Meanwhile, AFM measurements verified that the average surface roughness value increased between 0.06 μm and 5.9 µm, indicating an acidic attack by these acidic soil particles leading to the heterogeneous formation with some defects at random positions on this pipeline surface. The intergranular corrosion mainly contributed to this phenomenon along this pipeline and resulted in a progressive induction of non-uniform and pitting corrosion products.
Submersed downhole pump systems used in oil industry field are working and subjected to attacker environment. Rich aquas, chloride, and sulfide environments present a tough chemical condition. This work investigated a failure case study of two submersed downhole pumps that were worked in sea water in oil industry. Pump 1 and pump 2 failed after 196 and 60 days, respectively. Every pump had head and hosing made from carbon steel and compression ring made from stainless steel. Compression ring was not affected by corrosion, but head and housing were. Investigations were made for carbon steel head and housing by mechanical analysis, visual examination, optical microscope, and scanning electron microscope (SEM) for imaging and EDS. Results show a corrosion for the whole surface of two pumps and pitting corrosion in many positions. Many corrosion products are formed such as FeCO3, Fe2O3, and FeCl3. The corrosive products were the main reason for failure which formed due to working conditions and environment.
Purpose
The purpose of this work is to design the wire beam electrode (WBE) of P110 steel and study its corrosion behavior and mechanism under high temperature and pressure.
Design/methodology/approach
Packaging materials of the new type P110 steel WBE and high pressure stable WBE structure were designed. A metallurgical microscope (XJP-3C) and scanning electron microscopy (EV0 MA15 Zeiss) with an energy dispersive spectrometer were used to analyze the microstructure and composition of the P110 steel. The electrochemical workstation (CS310, CorrTest Instrument Co., Ltd) with a WBE potential and current scanner was used to analyze the corrosion mechanism of P110 steel.
Findings
According to the analysis of Nyquist plots at different temperatures, the corrosion resistance of P110 steel decreases with the increase of temperature under atmospheric pressure. In addition, R p of P110 steel under high pressure is maintained in the range of 200 ∼ 375 Ωcm ² , while that under atmospheric pressure is maintained in the range of 20 ∼ 160 Ωcm ² , indicating that the corrosion products on P110 steel under high pressure is denser, which improves the corrosion resistance of P110 steel to a certain extent.
Originality/value
The WBE applied in high temperature and pressure environment is in blank. This work designed and prepared a WBE of P110 steel for high temperature and pressure environment, and the corrosion mechanism of P110 steel was revealed by using the designed WBE.
The overall safety of anchorage engineering is jeopardized by the corrosion failure of low-carbon steel anchor bolts in a complicated geotechnical environment. To research the corrosion behaviour of low-carbon steel anchor bolts in carbonaceous mudstone slopes and to reveal the corrosion characteristics and mechanism of low-carbon steel anchor bolts under different corrosion time, solution corrosion, electrochemical corrosion and microscopic tests of low-carbon steel anchor bolts were carried out using a carbonaceous mudstone soaking solution and low-carbon steel anchor bolts as corrosion specimens. The results show that the low-carbon steel anchor bolts undergo obvious electrochemical corrosion in the carbonaceous mudstone environment. The corrosion product colour gradually deepened and the corrosion area gradually increased with increasing corrosion time. In the early stage of corrosion (0–10 d), the corrosion rate per unit area rapidly increased, and a thin oxide layer formed on the surface of the low-carbon steel anchor bolts. However, with the oxidation of Fe ions on the surface of the low-carbon steel anchor bolt body, the oxide film was gradually destroyed, resulting in the accumulation of corrosion products on the entire low-carbon steel anchor bolt surface. At this time, the entire reaction process was dominated by charge transfer and substance transfer.
A large-area laser-clad coating was realized by overlapping laser tracks and thus presents overlap and non-overlap zones on the surface. The microstructure and corrosion behaviors of the overlap and non-overlap zones of the multi-track laser-clad nickel-based alloy coating at various flow rates and impact angles were investigated. Results indicated that overlap zone presented coarse columnar dendrites rather than cellular structures. The primary phases were mainly composed of γ-Ni, and the precipitation at the grain boundary was Ni6Mo6C. At the impact angle of 60° and flow rate of 6 m/s, overlap zone showed 2.0 × 10–7 A/cm² higher stable potentiostatic polarization current density at passivation film destruction and furrow formation than non-overlap zone. The increase content of Mox+ (Mo) in non-overlap zone was 4.38% more than that in overlap zone after corrosion indicating the better Cl⁻ corrosion resistance. The current densities increased with the enhanced flow rate. At the impact angle of 60°, the flow rate increased from 1 to 6 m/s, and the potentiostatic current density increased by 3.0 × 10–7–3.7 × 10–7 A/cm². With the increase of the impact angle, the stable current densities increased first and then decreased. And the surface morphology changed from long and shallow ravines to short deep gully.
