Severe Pitting Research Articles

Wear and corrosion properties of mechanically coated 316 stainless Steel-TiC nanocomposites

The mechanical coating (MC) method was used to deposit 316 stainless steel (SS316), TiC, and SS 316-TiC nanocomposite coatings on SS 316 substrates using a ball mill machine at milling durations of 1, 2, 5, 10, and 15 h using relatively cheap and abundant raw material. The chemical composition of the SS 316, TiC, and SS 316-xTiC (x = 20, 50, 80 wt%) nanocomposite coatings deposited by the mechanical coating method has been investigated and the hardness values and the wear and corrosion mechanisms were presented. Dense and uniform coatings were obtained using a ball-to-powder weight ratio (BPR) of 20:1 and an MC duration of 5 h. Among the samples, the SS316-20 wt%TiC coating exhibited the best wear and corrosion resistance. The least mean coefficient of friction was 0.3 for the SS316-20 wt%TiC deposited sample while the largest mean coefficient was for the SS316-80 % TiC sample to be 0.76. The SS 316-20 wt% TiC sample had the lowest wear rate where the highest value was for the %100SS 316 sample being 0.36 × 10−6 and 19 × 10−6 (mm3/Nm), respectively. Corrosion tests revealed that the SS316-20%TiC sample had the best corrosion resistance among the composite samples having a corrosion resistance of 4.9358 μm/Y. The corrosion resistance decreased with the increase of TiC whereas the 80 % TiC coating had severe pitting. Cracks and pores present in the non-uniform 100 % TiC coating resulted in lower corrosion resistance compared to the 100 % SS 316 and composite coatings.

Microstructure and properties of a HIP manufactured SiCp reinforced high alloyed Al–Zn–Mg–Cu–Zr–Ti aluminum matrix composite

In this study, a hot isostatic pressing (HIP) manufactured SiC particles (SiCp) reinforced high alloyed Al–Zn–Mg–Cu–Zr–Ti aluminum matrix composite was fabricated through ball-milling, HIP, homogenization, hot extrusion, solution treatment, and aging treatment. The results showed the presence of an interfacial reaction layer, MgAl2O4, around the SiCp, which enhanced the bonding between the particles and the matrix. The aging treatment resulted in the formation of different aging precipitates, which were featured by GP zone for T4, GP zone + η' (metastable MgZn2) + η (stable MgZn2) for T6 and GP zone + η' (metastable MgZn2) for T6I4. The composite samples of T4, T6, and T6I4 exhibited different mechanical properties. Specifically, the elastic modulus was measured as 102.9, 103.4, and 102.3 GPa, the yield strength was 685.3, 598.1, and 619.7 MPa, the ultimate tensile strength was 713.6, 618.9, and 633.3 MPa, and the elongation was 2.2%, 1.8%, and 2.8%, respectively. Furthermore, the corrosion behavior of the composite was evaluated through electrochemical, intergranular corrosion, and exfoliation corrosion. The corrosion current density was found to be 3.17 × 10−7, 4.97 × 10−7, and 3.67 × 10−7 A cm−2, the corrosion potential was measured as −0.70, −0.81, and −0.56 V, and the maximum intergranular corrosion depth was 139.9, 167.8, and 106.2 μm for T4, T6, and T6I4, respectively. The severity of exfoliation corrosion varied, with T4 showing severe pitting, T6 exhibiting moderate pitting, and T6I4 displaying slight pitting. The strengthening mechanism and load transfer strengthening of the composites were discussed in detail based on theoretical calculations, and the anti-corrosion mechanisms were also analyzed.

Enhancing electrochemical corrosion resistance in Al–6Ni alloys through trace Sc additions

Al–Ni-Sc alloys exhibit superior mechanical properties at both room and elevated temperatures, owing to the high thermal and chemical stability of Al3Ni microfibers, and Al3Sc nanoprecipitates. This study explores the impact of scandium additions (0.2 and 0.4 wt%) in eutectic Al–6Ni casting alloys and the influence of aging treatment on electrochemical corrosion behavior in a 0.05 M NaCl solution. Scandium addition did not alter the polarization curve direction but reduced the anodic current density, slowing corrosion. Scandium strengthened the passive film, evident in Electrochemical Impedance Spectroscopy (EIS) with higher Rp values. Sc addition influences the susceptibility to localized corrosion in Al–Ni alloys by promoting the coherence of passive films through the formation of Al3Sc nanoprecipitates and affecting the distribution of Al3Ni. XPS results show that as-aged Sc-containing increases the density of coherent Al3Sc nanoprecipitates, which could result in the formation of Sc2O3 film along with films like Ni2O3 and Al2O3. These synergistic effects contribute to improving the overall corrosion resistance with Sc additions subjected to aging treatment. The microgalvanic effects between the matrix and reinforcement phases, as a result of the formation of nobler Al3Ni and Al3Sc that serve as cathodes within anode Al matrix, cause severe pitting. Nevertheless, after aged treatment, the corrosion resistance dramatically drops for alloys with 0.2 wt% Sc and remains unchanged for 0.4 wt% Sc, due to higher density of nobler Al3Sc nanoprecipitates phase that can counteract the microgalvanic effects and lead to less extensive pitting than as-aged Al–6Ni-0.2Sc.

Effect of Y Contents on the Microstructure, Mechanical Properties, and Corrosion Behavior of Biomedical Mg–0.5Zn Alloy

The effects of Y contents on the microstructure, mechanical properties, and corrosion resistance of biomedical Mg–0.5Zn alloy are investigated. In the results, it is shown that an increase in Y content leads to a growth in the amount of the second phase and a decrease in the spacing of the secondary dendrite arms. Additionally, the second phase changes from a uniformly dispersed point‐like shape to a semicontinuous reticular distribution. Meanwhile, the addition of Y obviously reduces the dendritic organization and this contributes to the improvement of mechanical properties. The corrosion resistance of the alloys increased first when Y content is 2 wt% at most, and then decreases in Mg–3Y–0.5Zn alloy. The gradual improvement of corrosion resistance in Mg–1Y–0.5Zn and Mg–2Y–0.5Zn is closely related to the formation of the compact corrosion layer including Y element, while the sudden drop corrosion resistance of Mg–3Y–0.5Zn alloy is mainly attributed to the presence of a great deal of semicontinuous long‐period stacked order and its excessive negative potential compared with Mg matrix, which leads to a severe pitting.

Stress corrosion cracking behavior and mechanism of 2205 duplex stainless steel under applied polarization potentials

In this work, a non-steady electrochemical model for assessing stress corrosion cracking (SCC) of 2205 duplex stainless steel (DSS) under applied polarization potentials was proposed, and the SCC mechanism was revealed. With the negative shift of potentials, hydrogen enhances SCC susceptibility by deteriorating passive film, inhibiting repassivation and causing serious damage. In particular, at −850 mV (vs. SCE), the synergetic effect of anodic dissolution (AD) and hydrogen embrittlement (HE) causes severe pitting and SCC. The negative shift of applied potentials changes the preferential pit/SCC initiation site due to high hydrogen concentration in austenite.

Effect of water vapor content on the corrosion mechanism of HR3C in simulated oxy-coal combustion environment

The corrosion performance of the HR3C steels covered with salt deposition (Na2SO4:K2SO4 = 1:1) was investigated under various water vapor content at 700 °C. Results show that the HR3C alloy undergoes severe pitting and sulfidation in a dry corrosive atmosphere (0.5SO2-4O2-CO2) and the corrosion products are peculiarly prone to peel off. In comparison, the corrosion behavior is gradually mitigated with increasing water vapor content. In highly humid corrosive gas (0.5SO2-4O2-20H2O-CO2), the corrosion degree is remarkably faint and the dominant corrosion mode is oxidation. The mechanism responsible for the transition of corrosion mode as water vapor content varied is discussed in detail.

Binary Mg-1 at%Gd alloy anode for high-performance rechargeable magnesium batteries.

Rechargeable magnesium batteries (RMBs) become a highly promising candidate for the large-scale energy storage system by right of the high volumetric capacity, intrinsic safety and abundant resources of Mg anode. However, the uneven Mg stripping and large overpotential will cause a severe pitting perforation and the followed failure of Mg anode. Herein, we proposed a high-performance binary Mg-1 at% Gd alloy anode prepared by the melting and hot extrusion. The introduction of 1 at% Gd element can effectively reduce the Mg2+ diffusion energy barrier (0.34 eV) on alloy surface and induces the formation of a robust and low-resistance electrolyte/anode interphase, thus enabling a uniform and fast Mg plating/stripping. As a result, the Mg-1 at.% Gd anode displays a largely enhanced life of 220 h and a low overpotential of 213 mV at a high current density of 5.0 mA cm-2 with 2.5 mAh cm-2 . Moreover, the assembled Mg-1 at.% Gd//Mo6 S8 full cell delivers a high rate performance (73.5 mAh g-1 at 5 C) and ultralong cycling stability of 8000 cycles at 5 C. This work brings new insights to design the new-type and practical Mg alloy anodes for commercial RMBs.

Enhancing Surface Integrity of Micro-Holes Machined on Inconel 718 using Shaped Tube Electrochemical Machining via Hydroxide Mixing

This research explores enhancing surface integrity of high aspect ratio (AR>5) micro-holes machined on Inconel 718 using Shaped Tube Electrochemical Machining (STEM) by mixing limited amount of metal hydroxides in the different electrolyte solutions. Typically, STEM employs hazardous acid solutions. These solutions cause machine corrosion, environmental risks, and harm to operators. This research aims to explore eco-friendly and safe alternatives. The efficacy of adding NaOH or KOH to eco-friendly neutral aqueous solutions of NaCl, KBr, and NaNO3 on machined surfaces is expounded. We assess electrolyte mixing parameters, including concentration and composition, and explore the effects of varying electrolyte temperature, voltage, and tool feed rate. Surface assessment uses SEM, EDX, XRD, and profilometry. Results reveal that adding hydroxides to neutral salt solutions improves surface roughness and reduces pitting. Hydroxide ions aid in dissolving oxide films during STEM of Inconel 718. Under specific conditions (9 g l−1, 18°C, 8 V, 0.8 mm min−1), NO3│OH yielded the lowest Ra (1.64 μm), while Br│OH resulted in the highest Ra (2.14 μm) with pitting, cracks, and deposits. NO3│OH exhibited a 25% decrease in Ra when a hydroxide concentration rise from 3 g l−1 to 15 g l−1. This research supports eco-friendly STEM for improved surface quality without process performance compromise.

Corrosion form transition of mooring chain in simulated deep-sea environments: Remarkable roles of dissolved oxygen and hydrostatic pressure

The corrosion form and mechanical properties deterioration of mooring chain steel in simulated deep-sea environments were investigated. With the increase of ocean depth, not only the pressure increases, but also the dissolved oxygen content decreases. These two factors affect corrosion evolution of mooring chain steel in simulated deep-sea environments, which was studied for the first time. Compared with uniform corrosion of mooring chain steel in shallow sea with sufficient oxygen, low dissolved oxygen leads to the corrosion dominated by pitting with pit covers. Meanwhile, hydrostatic pressure distinctly accelerates pitting initiation and propagation. The higher the hydrostatic pressure is, the more serious the pitting is. For failure mechanism of unstressed mooring chain steel serving in simulated deep-sea environments, both absorbed hydrogen and corrosion morphology can degrade the ductility of mooring chain steel, in which the leading factor depends on the service time. The severe pitting is the main factor and causes remarkable ductility loss of the steel after long-term immersion. But hydrogen plays an important role on elongation loss in early stage.

Metallurgical Failure Analysis of Closed Water Circuit Containing Molybdate-Based Inhibitor

In this work, two industrial heating/cooling circuits are compared. One of the two systems failed in a short time showing severe corrosion damage and a through thickness crack close to one of the welds. The main difference between the circuits is the presence of a sodium molybdate-based corrosion inhibitor in the damaged one. The addition of these substances is very frequent in such applications, and they generally work very well in preventing serious corrosion attacks. Nevertheless, the technical literature reports other cases in which systems working with fluids containing such inhibitors failed prematurely. The authors performed a failure analysis of the damaged circuit focusing their attention on the regions where fluid leaks were observed because of through thickness cracks. This damage was located close to the pipe–flange weld. These zones were investigated by visual examination, radiographic and scanning electron microscope (SEM) analyses, metallographic observations by light optical microscope (LOM), Vickers micro-hardness tests and optical emission spectroscopy (OES) chemical analysis. The failure was related to the presence of severe pitting and crevice corrosion in the welded areas with the final activation of a further critical corrosion mechanism, i.e., stress corrosion cracking (SCC). In order to explain the shorter working life of the failed system, a physical model of the corrosion mechanisms acting on the two circuits was proposed.

Molecular and biological characterization of a novel citrus tristeza virus isolate that causes severe symptoms in Citrus junos cv. Ziyangxiangcheng.

The complete genomic sequence of a novel citrus tristeza virus (CTV) isolate, CT91-A1, from Orah tangor grafted on Citrus junos cv. Ziyangxiangcheng rootstock in China was determined by transcriptome sequencing. Sequence alignments showed that isolate CT91-A1 shared 83.3 to 95.5% nucleotide sequence identity with extant CTV genotypes at the whole-genome level, with the highest similarity to the S1 genotype. Phylogenetic analysis revealed that CT91-A1 clustered in a unique subclade with the S1 genotype. Isolate CT91-A1 induced severe stem pitting in Mexican lime and C. junos cv. Ziyangxiangcheng and moderate stem pitting in Guanximiyou pummelo and Duncan grapefruit. It was successfully transmitted by Aphis citricidus, and it can potentially cause significant damage to the citrus industry in China.

Effect of alloying element content on anaerobic microbiologically influenced corrosion sensitivity of stainless steels in enriched artificial seawater

Stainless steels (SS) are not immune to microbiologically influenced corrosion (MIC) especially in the presence of sulfate reducing bacteria (SRB). It is necessary to study the influence of alloying elements on the MIC. SRB MIC behaviors of four stainless steels (2205 SS, 316L SS, 304 SS, and 410 SS), with different alloying element compositions were compared after 14 days of incubation at 37°C in enriched artificial seawater inoculated with Desulfovibrio sp. The sessile cell sequence was 410 SS > 316L SS > 304 SS > 2205 SS, inversely proportional to Cr content. The uniform corrosion rate (based on weight loss) sequence was 410 SS > 304 SS > 316L SS > 2205 SS, which matches the pitting resistance equivalent number (PREN) sequence inversely. 410 SS with the lowest Cr and Mo contents suffered the most severe pitting, with pit depth of 35 μm and weight loss of 0.75 mg/cm2 (0.91 mm/a pitting rate and 25 μm/a uniform corrosion rate). The other three stainless steels with higher Cr and Mo contents suffered only metastable pits. The semiconductor characteristics and the re-passivation abilities of the passive films were found to be affected by Cr and Mo contents.

Corrosion Failure Analysis of CuNi 90/10 on Seawater Fire Protection System

The failure analysis of a seawater fire protection system of oil and gas processing facility was observed in this paper. The fire protection pipe line & hull seawater filter were made of CuNi 90/10. Severe deep pits and fracture were observed at bottom of jockey pump spool pipe and hull seawater filter. Visual observation, scanning electron microscope, energy dispersive spectroscopy, x-ray diffractometry were employed in the present failure analysis. The oxygen exposure on CuNi 90/10 of Seawater Fire Protection system had a significant impact on failure and was exacerbated by the presence of chloride exposure.

Metallurgical characterization of a failed A106 Gr-B carbon steel welded condensate pipeline in a petroleum refinery

A condensate pipeline made of carbon steel alloy with grade A106-Gr.B, had a leakage in the form of a pinhole at the girth weld after 16 years of operation. Visual examination, optical and scanning electron microscopy (SEM), coupled with energy-dispersive X-ray spectroscopy (EDS), chemical analysis, and hardness measurements were performed on the failed pipeline samples. Visual examination of the inner surface of the circumferential weld line showed many types of welding defects, as well as severe localized corrosion pits in the weld zone at the bottom of the pipe surface. The microscopic analysis shows that the localized corrosion attack is the root cause of the pipe failure. XRD patterns of the inner surface of the failed pipe emphasizes a formation of corrosion products of iron oxyhydroxides such as Lepiodocrocite (Fe + 3O(OH)), and Goethite (FeO(OH)). Additionally, the foreign elements of aluminum, and chlorine, detected by the EDS analytical results promote under-deposit corrosion, particularly in regions with stagnant water, i.e., at 6 O'clock pipe position.

Li Morphology Evolution during Initial Cycling in a Gel Composite Electrolyte

Li metal anodes are the potential solution for high-energy batteries. One of the challenges of applying such a high-energy anode is Li dendrite growth, which results in short-circuit and thermal runaway. Current battery research focuses on developing solid electrolytes to serve as a physical barrier to prevent dendrite growth. However, the Li morphology change during plating and stripping, and the mechanisms of how Li dendrite grows and propagates into a complex composite solid electrolyte are poorly understood. Understanding and controlling Li morphology evolution, dendrite formation, and growth during cycling are crucial to developing dendrite suppression strategies for solid electrolytes and enabling high-energy lithium metal batteries.In this work, Li morphology evolution during initial cycling in a crosslinked PEO-based gel composite electrolyte full cell with NMC 811 cathode is monitored via post-mortem SEM. The results show that severe surface pitting occurs as early as the second stripping cycle. Pit formation and continuous dissolution is the main cause of Li surface roughening and dendrite growth mechanism in the model gel composite electrolyte. Comparing Li dendrite growth mechanisms in liquid, polymer, and solid electrolytes, the observed dendrite growth mechanism resembles that of the liquid electrolyte the most. This study suggests that strategies to improve the electrochemical reversibility of electrodeposited Li reported in liquid electrolytes to control Li morphology and prevent dendrite growth may be transferrable in a gel electrolyte.This work is sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory (ORNL), managed by UT-Battelle, LLC for the U.S. Department of Energy under Contract No. DE-AC05-00OR22725. Part of the measurements was performed at the Center for Nanophase Materials Sciences (CNMS), which is sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences.

Electroless Nickel Phosphorus Coatings to Mitigate the Corrosion of Construction Steel

Reinforced concrete is widely used in structures and construction, but its durability is limited due to corrosion of the embedded steel rebars. Thus, mitigation of corrosion of construction steel rebars is an important area of research. The present work reports the ability of electroless nickel phosphorus coating for corrosion protection of Fe-600-grade steel rebars used for construction purposes in chloride and sulphate environment. The coating deposited on Fe-600 rebar was Ni-P and was subjected to electrochemical tests in 3.5% NaCl and 0.5M H2SO4. Severe corrosion pitting and cracking were observed for the uncoated rebar while Ni-P coating showed nobler corrosion potential and low corrosion current density in the corrosive environments.

Investigations of cavitation erosion and wear resistance of cermet coatings manufactured by HVOF spraying

This work studies the effect of mechanical properties and microstructure on sliding wear and cavitation erosion behaviors of cermet coatings deposited via high velocity oxy-fuel (HVOF) spraying on AZ31 magnesium substrate. Cavitation tests indicated that WC-Co-Cr cermet had superior resistance to cavitation erosion than WC-Cr3C2-Ni, WC-Co coatings, and far better resistance than the AZ31 expressed by the volume material loss 3.74 mm3, 6.99 mm3, 10.30 mm3, and 108.82 mm3, respectively. WC-Co-Cr coating’s erosion mechanism exhibited uniform material removal, which slows the erosion rate. The CoCr binder prevented severe surface pitting and the detachment of the WC-Co-Cr cermet material in massive chunks which was observed for WC-Co and WC-Cr3C2-Ni coatings. Cermet coatings microstructure discontinuities such as pores and ceramic-metallic phase interfaces are the centers of material erosion. No clear correlation between the erosion behavior and mechanical properties of coatings was revealed. Contrary to that, sliding wear results were strongly related to the mechanical properties. The WC-Co-Cr and WC-Co samples exhibited higher hardness and higher values of Young’s modulus than the WC-Cr3C2-Ni one. The generated stresses with lower values of hardness and Young’s modulus for the WC-Cr3C2-Ni sample resulted in a higher wear factor, approx. 1·10−7 mm3·N−1·m−1. For the harder samples, which exhibited higher stiffness (WC-Co-Cr and WC-Co), this type of wear resulted in lower values of the wear factor: 6·10−8 mm3·N−1·m−1 and 9·10−8 mm3·N−1·m−1, respectively. Deposition of the cermet coatings effectively protected the magnesium substrate, which shows low resistance to cavitation erosion and sliding wear when uncoated.

Failure analysis of a natural gas transmission X60 steel pipeline

PurposeThis paper aims to investigate the reason for natural gas leakage from transmission pipelines between Linyi and Shouguang in China during sealing tests, explore the failure mechanism and provide a reference for taking reasonable measures to prevent such accidents.Design/methodology/approachFailure analysis for the steel pipe has been addressed with different methods, such as microstructure analysis, inclusion analysis, corrosion product analysis, macro- and micro-morphology analyses and bacterially catalyzed experiments.FindingsSeveral bulges were observed, especially at the bottom of the steel pipe sample, with the distribution and positioning not related to the weld. The inner surface of the steel pipe was severely corroded, and the oxide scale was flaking in many places. The greatest corrosion area was identified at the bottom of the steel pipe near the gas leakage point. Severe pitting and perforation corrosion in the pipeline were observed, and the main corrosion reaction products were Fe3O4, FeO and FeS. The grain orientation distribution near the crack (coarse grains <101> and fine grains <111> at the microcrack tip) indicates that fine grains may be beneficial in hindering crack propagation.Originality/valueThe principal mechanism for the corrosion failure is supposed to be due to the interaction of chloride ions with the sulfate-reducing microorganisms present and the stress corrosion cracking by chloride and sulfide formed by the sulfate-reducing microorganisms.

Carbon fiber damage evolution under flame attack and the role of impurities

AbstractCarbon fibers (CFs) are prone to extensive oxidation under fire attack, for instance, in an aircraft fire scenario. This work addresses the damage mechanisms observed on polyacrylonitrile (PAN)‐based CFs with different microstructure exposed to open flames. A fixed‐point technique was developed to follow‐up individual CFs by means of time‐controlled insertion into premixed methane/air flames, followed by scanning electron microscopy (SEM) and energy‐dispersive X‐ray spectroscopy (EDS) analyses. Besides diameter reduction, three localized damage mechanisms were discerned in the presence of impurities, which were quantified by neutron activation analysis (NAA). Severe pitting was ascribed to catalytic oxidation mainly caused by alkali and alkaline earth metals. After an initial period where catalytic reactions between impurities and the carbon surface dominate, the flame stoichiometry governed the CF gasification process, with lean flames being much more aggressive than rich ones. A second mechanism, channeling, was caused by mobile metallic impurities. Some impurities showed an opposite effect, lowering reactivity and thus preventing further catalysis. Amorphous damage with a skin‐peeling effect is believed to be the result of localized impurities at high concentrations and microstructural variations. Hindrance or synergistic effects between impurities are discussed. Finally, apparent axial pit growth rates were determined and compared with other carbonaceous materials, revealing a strong influence of impurities and the flame reactive atmosphere on CF oxidation.

Contribution of Diffusing Hydrogen to Anodic Processes and Pitting for Iron in Chloride-Bearing Bicarbonate Solutions

The effects of diffusing hydrogen atoms on anodic processes and pitting corrosion for iron in chloride-bearing bicarbonate solutions were studied with a dual cell for realizing the hydrogen diffusing and electrochemical measurements simultaneously. A high concentration of chloride in solution, precleaning, and diffusing hydrogen in iron can move the open-circuit state from a passive state to an active dissolution state. Potentodynamic anodic polarization curves show that the effect of diffusing hydrogen is strongly dependent on the chloride concentration in the solution. The diffusing hydrogen atoms enhance the anodic reaction before the oxygen evolution potential when the chloride concentration is low while they enhance the anodic reaction in the overall potential range when the chloride concentration is high. In addition, diffusing hydrogen atoms slow down the anodic reaction in the first current plateau regime while not significantly affecting the other potential regimes if the chloride concentration is sufficiently high. Comparisons of the results from the hydrogen-diffusing electrodes with those from the precleaned electrodes facilitate clarifying the roles of diffusing hydrogen atoms in anodic reactions. For the hydrogen-diffusing electrode, the occurrence of the active dissolution regime is mainly from the surface cleaning effect, and the enhanced anodic reaction in the transition regime, prepassive regime, passive film growth regime, passive regime, and in some cases, transpassive regime, is due to both the electrode kinetics and the surface cleaning effect. Diffusing hydrogen would retard the anodic reaction in a specific potential regime through its combined effect with high concentration chlorides. More severe pitting is generally observed for the precleaned electrodes and the hydrogen diffusing than for the noncharged electrode. Depending on the applied potential and time as well as the chloride concentration, the hydrogen-diffusing electrode would show more extensive or severe pitting than the precleaned electrode, with some exceptions showing less severe pitting.