Corrosion Mechanism Research Articles

Study on corrosion mechanism of laser-clad Ni-WxC coating by in-situ electrochemical method under high temperature and pressure environment

Corrosion protection of oil and gas equipment by laser cladding technology has emerged as a crucial method to reduce costs and increase efficiency. The in-situ electrochemical method was employed to investigate the microstructure evolution and corrosion mechanisms of laser-clad Ni1725-WxC coatings under high temperature and pressure environment. The coating is composed of cellular γ-Ni (W, Cr, Fe), block W2C, WC/W2C eutectic structure with a shell of WC, and small amount of CrxCy (Cr7C3/Cr23C6) in Ni1725 matrix. The corrosion resistance of the coating is worsened with increasing temperature under in-situ electrochemical method owing to reduced reaction activation energy and increased transfer rate. Furthermore, the surface potentials of the coating follow the order: E1 (WC shell) > E2 (Ni1725 matrix (oxide)) > E3 (WC/W2C eutectic phase) > E4 (block W2C). Therefore, galvanic corrosion occurs between WC shell and Ni1725 matrix. W2C with lower potential corrodes preferentially as well at WC/W2C eutectic structure in WxC particle, which expands with increasing temperature to form a loose internal structure.

Corrosion resistance of pressure/pressureless sintered cemented carbides with/without graphene oxide in NaOH solution

The electrochemical corrosion performance of WC-Co hard alloy was studied under pressure/pressureless sintering and conditions with/without graphene oxide added. Three electrochemical testing methods were used to evaluate the corrosion behavior: open circuit potential, electrochemical impedance spectroscopy, and dynamic potential polarization. The corrosion resistance of the alloy was compared using three parameters of corrosion potential, corrosion current density, and total impedance. The corrosion mechanism was studied by observing the surface morphology of corroded alloy using scanning electron microscopy and analyzing the surface corrosion products using X-ray photoelectron spectroscopy. The results showed that pseudo-passivation phenomenon appeared in the potentiodynamic polarization curve of the hard alloy in the sodium hydroxide solution. The corrosion behavior was mainly controlled by anodic dissolution, with the dissolution of WC phase being greater than that of Co phase. The corrosion resistant properties of the pressure sintered cemented carbide are higher than that of the pressure-less sintered cemented carbide respectively in NaOH solution, mainly because pressure increases the grain size and decreases the grain boundaries of cemented carbide, which can be regarded as the dislocation wall between grains and normally attacked by the serious corrosion preferentially.

TEM Analysis and Failure Mechanism Studies of Bromine-Induced Defects in Wafer Fabrication

In wafer fabrication, the contamination of halogen is commonly encountered, such as fluorine, chlorine, bromine. These contaminants can seriously impact product’s quality and yield. In the previous works, we have studied F and Cl-induced metal corrosion and failure mechanisms. In this paper, we will apply TEM analysis technique to study Br-indued corrosion and failure mechanism. Moreover, we will introduce a model of “Br-chain chemical reaction” to explain why even a little bit of Br contamination, it can cause very bad corrosion results, and the formation of the worm-like defects at the side of Al metal lines in wafer fabrication.

Enhanced high-temperature corrosion resistance of Cr-modified phosphate/aluminum powder composite coatings: Mechanisms and thermodynamic insights

Phosphate composite coatings are regarded as one of the tangible solutions for surface protection in salt spray environments, benefiting from their cost-effectiveness and prominent structure stability upon high-temperature exposure. However, rapid curing of these coatings often leads to crack formation, and the underlying corrosion mechanisms in service conditions remain insufficiently understood, limiting their practical applications. In this study, we developed chromium-incorporated phosphate/aluminum powder composite (Cr-P/Al) coatings and evaluated their corrosion resistance under alternating conditions of salt spray corrosion and oxidation at 450 °C. By integrating experimental results, ab initio calculations, and thermodynamic analysis, we demonstrate that the incorporation of Cr significantly enhances the performance of the P/Al coatings. The structural evolution was first revealed that Cr’s modification reduced tensile stress and prevented cracks in the coating. A mixed layer of amorphous oxides and phosphates forms on the surface of the Al powder, providing robust binding strength. A novel corrosion mechanism was identified that Cl2 and volatile chlorides facilitated the removal of Cl-. This process is more ineffective with Cr-P/Al coating, as amorphous Cr oxide has low reactivity at a high log[p(Cl2)] and low log[p(O2)] compared with amorphous Mg and Fe oxide, thereby enhancing the corrosion resistance of the coating. These coating densification methods and corrosion protection mechanisms provide a critical foundation for the future application of phosphate composite coatings.

Effect of sulfur on synergistic corrosion behavior of Q235 and 16Mn steel in sodium aluminate solution

In this study, the corrosion electrochemistry and corrosion behavior of two steels were studied under the simulated alumina production conditions. The corrosion rate of 16Mn steel is greater than that of Q235 steel. The effect of S2− concentration on corrosion rate was significantly higher than that of S2O32−. The synergistic corrosion rates of Q235 and 16Mn steels increase at first and then decrease with the sulfur content, and the peak value appears when the concentration of S2− and S2O32− is 4 g/L and 3 g/L respectively. There are two main types of corrosion products: one is surface octahedral grain, which is composed of Fe2O3, Fe3O4 and Al2O3.The other is the interlayer corrosion between the surface layer and the matrix, which is composed of FeS, FeS2 and NaFeO2.The formation mechanism of the corrosion and corrosion mechanism were obtained by analyzing the phenomenon of ion competitive adsorption. Further validation and analysis of ion competition adsorption phenomenon were conducted using first-principles calculations based on density functional theory (DFT). The formation of corrosion products on the steel surface was investigated at an ion level, and the adsorption energies of OH− and S2− at the top site of Fe(110) surface were calculated. It was found that S2− is more likely to be adsorbed on the Fe(110) surface compared to OH−. The corrosion mechanism of steel is discussed preliminarily.

Effect of surface orientation on the corrosion behavior of Ni-based single-crystal alloy in a simulated marine atmosphere at 750 °C

DD5 single-crystal alloy samples with different surface orientations were obtained by machining the alloy ingot perpendicular (PP) and parallel (P), respectively, to its solidification direction (SD). The corrosion behaviors of the PPSD and PSD alloy samples were investigated in the atmosphere of moist air + NaCl aerosol at 750 °C. Results showed that during initial corrosion, γ′ phase developed a thin NiO layer with Al internal corrosion product. However, a NiO nodule with an internal Cr2O3 layer was formed on γ phase. As corrosion progressed, the corrosion product gradually grew to a NiO/(Al, Cr)2O3 bilayer, accompanied by internal corrosion consisting of Al2O3. It was also found that the PSD sample with a lower fraction and smaller size of γ’ phases exhibited better corrosion resistance than the PPSD sample. The effect of alloy surface orientation on the corrosion mechanism was discussed.

On the Use of a Chloride or Fluoride Salt Fuel System in Advanced Molten Salt Reactors, Part 3; Radiation Damage

Structural materials in fast reactors with harsh radiation environments due to high energy neutrons—compared to thermal reactors—potentially suffer from a higher degree of radiation damage. This radiation damage can change the thermophysical and mechanical properties of materials and, as a result, alter their performance and effective lifetime, in some cases leading to their disintegration. These phenomena can jeopardize the safety of fast reactors and thus need to be investigated. In this study, the effect of radiation damage on the vessels of molten salt fast reactors (MSFR) was evaluated based on two fundamental radiation damage parameters: displacement per atom (dpa) and primary knock-on atom (pka). Following the previous part of this article (Parts 1 and 2), an iMAGINE reactor core design (University of Liverpool, UK—chloride-based salt fuel system) and an EVOL reactor core design (CNRS, Grenoble, France, fluoride-based salt fuel system) with stainless steel and nickel-based alloy material vessels, respectively, were considered as case studies. The SPECTER and SPECTRA-PKA codes and a PTRAC card of MCNPX, integrated with a module which has been developed in MATLAB, named PTRIM and SRIM-2013 (using binary collision approximation), were employed individually to calculate and compare dpa and PKA (this master module containing all three tools has been appended to the iMAGINE-3BIC package for future use during reactor operations). Additionally, SRIM-2013 was applied in a 3D simulation of a radiation damage map on a small sample of vessels based on the calculated PKA. Our results showed a higher degree of radiation damage in the iMAGINE vessel compared to the EVOL one, which could be expected due to the harder neutron flux spectrum of the iMAGINE core compared to EVOL. In addition, the nickel alloy vessel showed better radiation damage resistance against high energy neutrons compared to the stainless steel one, although more investigations are required on thermal neutrons and alloy corrosion mechanisms to determine the best material for use in MSFR vessels.

Corrosion mechanism of press-hardened steel with zinc coating in controlled atmospheric conditions: A laboratory investigation

The formation and evolution of corrosion products on zinc galvanized press-hardened steel during various atmospheric tests were studied. A high protective ability of the coating containing Zn-Fe intermetallics was shown. The composition models of the soluble and stable corrosion products were calculated. A significant effect of barrier corrosion products on corrosion resistance, especially simonkolleite, hydrozincite and dawsonite, was demonstrated. Exposure to constant high relative humidity resulted in the largest mass loss due to the accelerated formation of akaganeite. On the contrary, the presence of sulphates caused formation of additional barrier corrosion products and almost a threefold drop in mass loss.

Corrosion performance and mechanism of clay-lignin biocomposite: Effective bio based coating with strong adhesion character for extended carbon steel protection

The development of sustainable and eco-friendly anticorrosion coating for metal substrates is a pivotal advancement in various engineering fields. Hence, the novel sepiolite-lignin (SP-L) and bentonite-lignin (BN-L) biocomposites were successfully introduced in an alkyd resin 5.0 wt% and applied on carbon steel (CS), to prepare the alkyd SP-L (A/SP-L) and BN-L (A/BN-L) coatings. Particle size and zeta potential measurements were conducted to determine the average particle size and assess the stability of the reinforcing pigments. The corrosion performance of A/SP-L and A/BN-L coatings revealed higher protection with an impedance modulus of about 5.18 × 105 Ω.cm² and 7.86 × 105 Ω.cm², respectively, after 6weeks of immersion in 3 % NaCl solution, measured by electrochemical impedance spectroscopy (EIS), which were extremely higher than the reference alkyd (RA) 1.13 × 103 Ω.cm². The adhesion of the three coated samples before and after immersion was assessed using pull-off test, while their hydrophobicity and impermeability were evaluated using saline corrosion and water absorption tests. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were utilized to examine the corrosion mechanism. The results demonstrated an excellent coating quality and interfacial adhesion against corrosion.

Electrochemical impedance spectroscopy measurements on time-variant systems: the case of the Volmer-Heyrovský corrosion reaction. Part I: theoretical description

One of the theoretical requirements of electrochemical impedance spectroscopy measure­ments is that the studied system should not be varying with time. Unfortunately, this is rarely the case of physical systems. In the literature, quite a few methods exist to check and correct a posteriori the effect of time-variance, allowing to use conventional equivalent circuit models to fit and interpret the data. We suggest a different approach where, for a given electro­chemical mechanism and specific experimental conditions, assuming stationarity during each measurement, a time- and frequency-dependent expression of the Faradaic impe­dance is derived from the kinetic equations. The case of a potential relaxation at zero current following an anodic steady-state polarization is considered for a system where a Volmer-Heyrovský corrosion mechanism is supposed to take place.

Revealing the mechanisms of exfoliation corrosion and stress corrosion cracking for an Al-Zn-Mg-Cu alloy after continuous retrogression and re-ageing treatment

Continuous retrogression and re-ageing (CRRA) treatment is designed to achieve an optimal balance between the strength and corrosion performance of an Al-Zn-Mg-Cu alloy. The findings suggest that intergranular corrosion predominantly affects the T6 sample, with extensive propagation into the bulk resulting in delamination and intergranular cracking. In contrast, crystallographic pitting dominates in the CRRA-treated sample, which effectively mitigates exfoliation corrosion and suppresses intergranular cracking. The different corrosion resistance between the T6 sample and the CRRA-treated sample is attributed to the disparate distribution of Cu in the alloy, which influences the corrosion rate, the types of corrosion and corrosion propagation path.

Investigation on localized corrosion behavior of pipeline steel under AC interference in alkaline earth metal environment using wire beam electrode

The localized corrosion behavior of X65 steel under AC interference in alkaline earth metal environment was investigated using the detachable wire beam electrode (WBE). The AC/DC current distribution, electrochemical properties, and elemental distribution were traced through the WBE to characterize the localized corrosion behavior and mechanism. The results show that hydrogen evolution under high cathodic protection (CP) conditions leads to an uneven distribution of calcareous deposits, and areas not covered by calcareous deposits have higher JAC and Cl− concentrations. The synergistic effect of Fe3O4 dissolution reprecipitation process, hydrogen evolution and Cl− leads to severe localized corrosion.

Quantification of Corrosion on Cu Wire Bonding on Ag-Plated Lead Frame in HCl for Automotive Electronic Application

Copper (Cu) wire bonding has been widely used in automotive electronics as an interconnection technology. However, Cu wire bonding faces long-term reliability challenges due to corrosion, particularly when exposed to harsh environments. While the corrosion behavior and mechanisms of bulk-sized Cu metal are well studied, the corrosion behavior of submicron-sized Cu wire bonding in miniaturized components remains unclear. This study investigates the corrosion susceptibility of Cu wire with a 1 mil diameter, bonded to an Ag-plated leadframe in a small-outline transistor (SOT-23) package, commonly used in automotive electronics. The Cu wire bonds were subjected to varying concentrations of hydrochloric acid (HCl), specifically 3 M, 5 M, and 7 M, for exposure durations of 6, 12, and 18 hours. The samples were characterized using a field emission scanning electron microscope to observe the microstructure, and ImageJ software was used to quantify the corrosion of the Cu wire bonds. The findings show that the Cu wire bonding is susceptible to corrosion when exposed to high concentrations of HCl. The corrosion of the microstructure became more severe with increasing HCl concentration and exposure time. The affected area of the Cu wire bonding was 21% after 6 hours of exposure to 3 M HCl, increasing to 100% after 18 hours of exposure to 7 M HCl. This study reveals that the corrosion behavior of Cu wire bonding is a combination of selective and pitting-like corrosion, resulting in localized surface degradation rather than uniform corrosion. These findings provide valuable insights into the corrosion behavior of 1 mil Cu wire bonding in SOT-23 packages under highly corrosive environments.

Failure Analysis of a Welded 316L Stainless-Steel Stack with Premature Damage Due to Stress-Corrosion Cracking

AbstractThis study analyzed the premature failure of a stainless-steel stack obtained from a mining company. The stack was manufactured using ASTM A240 Type 316L stainless steel. After one year of its service, massive leakages and cracks were observed near the welds. Following a visual examination of the stack, a representative sample was extracted and analyzed using visual and radiographic inspection, metallographic examination, scanning electron microscopy, energy-dispersive spectrometry, optical emission spectrometry, ferrite number analysis, and leak testing. Furthermore, corrosion mechanisms and the sequence of events leading to failure were determined. Two different mechanisms were identified: acid dew point corrosion caused by the condensation of H2SO4 and HCl at the inner walls of the chimney, followed by stress-corrosion cracking near the welded joints.

Corrosion behavior and mechanism of Cr10Mo1 steel subjected to different corrosive ions in simulated concrete pore solution

The corrosion of pre-passivated Cr10Mo1 steels in simulated concrete pore solution of saturated Ca(OH)2 induced by different corrosive ions were investigated, namely Cl−, SO2- 4, and combination of Cl− and SO2- 4. Electrochemical methods, Pourbaix analysis of Fe–Cr–H2O system and DFT calculation were adopted to characterize corrosion behavior and reveal underlying mechanism. Results showed that while sulfate may induce corrosion at higher threshold value, the scenario of chloride alone leads to lowest corrosion potential, linear polarization resistance and highest corrosion rate, and the presence of SO2- 4 ions mitigate corrosion risk under the coexistence condition of chloride and sulfate. A two-step reaction model of competitive adsorption-catalytic corrosion was proposed based on theoretical analysis and DFT calculation results.

Consecutive pozzolanic layerings to depress internal-sulfate-attack corrosion of OPC by phosphogypsum-based cold bonded aggregates

Phosphogypsum-based cold bonded aggregates (PCBAs), as incorporates excessive soluble sulfate, potentially induce Internal Sulfate Attack (ISA) corrosion to OPC, which severely constrains its utilization and advancement. This work applies consecutive pelletization using pozzolanic layerings (fly ash (FA) and phosphorus slag (PS) basis) for surface modification. The basic, exterior hydration and microstructure properties of PCBAs, as well as the interfacial corrosions of PCBAs-OPC, are investigated via XRD, TG-DTG, X-CT, SEM-EDS, μ-XRD, and nanoindentation technologies. Results indicate the FA and PS layerings block sulfate leaching by 15–30%. When blended with OPC, these layerings capture releasable sulfate within PCBAs exterior via interfacial hydration that also depletes portlandite to generate tighter ITZ. Therefore, the reactive layerings effectively alleviate ISA corrosion via in-front blockage and back-end reaction, as supported by reduced sulfate ingress within 30–40 μm, less degradation products (ettringite and gypsum) formation, and improved hardness of vicinity OPC. The FA-based layering performs slightly poorer due to its lower density causing inefficient consolidation of PCBAs. Consequently in macroscopic, the ISA-inducing fissures of concrete surface are diminished, followed by improved 90-d compressive strength from 36.43 MPa to optimally 48.38 MPa. This study elucidates the rich-gypsum aggregates-type ISA corrosion mechanisms to OPC and proposes an instructive solution using pozzolanic layerings.

Investigation of Factors Affecting Corrosion Mechanisms in Latent Heat Thermal Energy Storage Systems

Concentrated Solar Power (CSP) plants integrated with Latent Heat Thermal Energy Storage (LHTES) systems offer a promising solution for dispatchability, reliability, and economic concerns generally associated with renewable energy technologies. These systems, however, require an operational life of up to 30 years to compete with power plant systems operating on fossil fuels. This is a significant challenge due to the high temperatures and corrosive eutectic salts utilised in LHTES systems. Additionally, these systems and its subcomponents are expected to be under varying degrees of stress due to the diurnal cyclic temperature variations inherent in the plant’s operational cycle. Hence, it is crucial to understand the various factors that can affect the operational life of materials used in such applications and conduct thorough material compatibility studies to assess the combined impact of these operating conditions on corrosion mechanisms. This study presents a novel static immersion test approach using modified Compact Tension (CT) specimens manufactured from 316L to investigate the effects of Na2CO3:NaCl (59.45:40.55 wt.%) salt, elevated temperatures (700 ℃ for up to 1000 hours), and stress on corrosion induced in the alloy. The post-exposure results are characterised with Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) shows that corrosion mechanisms are significantly affected by factors such as high operating temperatures leading to changes in both corrosion morphology and rate, high stresses causing localised preferential corrosion, as well as corrosive salt and oxygen availability affecting the type of corrosion induced.

Study on corrosion behavior Ⅱ of hot-dipped Zn-6Al-3Mg alloy coating: Surface oxide layer and ternary eutectic corrosion

The oxide layer and ternary eutectic of Zn–6Al–3Mg alloy coating have an important effect on its corrosion behavior and corrosion resistance, but the influence of oxide layer on the corrosion behavior of the coating and the internal corrosion mechanism of ternary eutectic structure are still unclear. In this study, the oxide layer and ternary eutectic of the coating were characterized in detail, and the corrosion behavior of the oxide layer and ternary eutectic in the environment containing Cl were studied based on first principles of density functional theory. The results show that the surface oxide layer can initially prevent the erosion of Cl-, MgZn2 in ternary eutectic preferentially corrodes after the oxide layer dissolves, corrosion products are formed.

Quantitative characterization on influence of surface particles on corrosion behavior of multiarc ion plated CrAlN coatings

Surface particles on multiarc ion plated coatings are common defects, and their influence on the service performance of coatings is rarely defined. The CrAlN coatings were deposited on the tungsten steel (YG8) substrates using multiarc ion plating. The effects of the substrate bias voltages and nitrogen flow rates on the quantity of the surface particles were investigated, and the influence of the surface particles on the corrosion resistance of the coatings is quantitatively characterized. The morphology of surface particles was characterized using a scanning electron microscope. The quantity of the surface particles was counted by image software. The corrosion resistance of the coatings was evaluated through an electrochemical workstation. The results show that the quantity of surface particles decreased with the increase in the substrate bias voltage and nitrogen flow rate. The corrosion resistance of the coatings showed a positive correlation with the quantity of the surface particles, and it decreased dramatically when the quantity of the surface particles exceeded 111/10 000 μm2. The corrosion mechanism of the coatings was attributed to the defect-induced pitting corrosion.

Advanced corrosion resistance and mechanistic insights of electroless Ni-P-PTFE coatings on L245NS substrate in H2S-saturated environments

The extraction and transportation of oil and gas pose significant challenges due to corrosive environments, particularly hydrogen sulfide (H2S) exposure. This study investigates the use of polytetrafluoroethylene (PTFE) to enhance the corrosion resistance of nickel‑phosphorus (NiP) coatings in H2S-rich environments. Electroless deposition was employed to prepare Ni-P/PTFE coatings, which were then subjected to simulated H2S corrosion tests. Results indicate that the incorporation of PTFE led to a more uniform NiP coating with reduced porosity, significantly improving corrosion resistance. The coatings exhibited enhanced protective performance by stabilizing corrosion product layers and preventing the formation of corrosion channels. Ni-P-PTFE coatings overcame the existing research challenge of NiP coatings' corrosion in H2S environments, showing no penetration of the corrosive medium into the substrate after 720 h of immersion. The corrosion rate of the coating is only 0.0261 mm/year, only 4.27 % of the corrosion rate of the L245NS substrate in the early stage of corrosion. Moreover, after characterization by SEM, XRD and XPS, it was found that the presence of PTFE altered the corrosion mechanism, promoting the formation of stable nickel sulfide and oxide layers on the surface. This study sheds light on the mechanisms underlying PTFE-enhanced corrosion resistance in NiP coatings, offering promising implications for extending the lifespan of equipment in the oil and gas industry.