Stainless Steel In Artificial Seawater Research Articles

Effect of CrYN/TiBN coating on friction performance and corrosion resistance of 316 stainless steel in artificial seawater

CrYN, TiBN, and CrYN/TiBN coatings were successfully deposited on 316 stainless steel substrates via multi-arc ion plating techniques to improve their wear and corrosion resistance properties in marine environments. The morphology, microstructure, friction performance, and corrosion resistance of the three coatings in artificial seawater were systematically studied. X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy investigations confirmed a dominant face-centered cubic CrN structure, accompanied by hexagonal TiB2 and amorphous BN in CrYN/TiBN coatings. The SEM cross-section shows that the TiBN and CrYN/TiBN coatings have a more compact cross-sectional structure than the CrYN monolayer coating. The CrYN/TiBN coatings exhibited the lowest smooth friction coefficient in artificial seawater, and the wear rate was ranked as TiBN < CrYN/TiBN < CrYN. Surface morphological studies performed after tribocorrosion revealed that the protection ability of all three coatings remained acceptable. The electrochemical test showed that the corrosion tendency was CrYN/TiBN < TiBN < CrYN, and the CrYN/TiBN coating had the best performance in the AC impedance spectrum and polarization curve.

Influence of artificial seawater on the VHCF behavior of different steels

AbstractThe fatigue properties of a high‐strength steel, a structural steel, and a duplex stainless steel in artificial seawater were investigated. Consequently, a test chamber for the existing ultrasonic test stand was implemented. The experiments were performed with smooth specimens at a loading with R = −1 up to 2 · 109 cycles. The specimens were fully submerged in artificial seawater. The fatigue data were statistically evaluated using the pearl string method and compared to different SN curves from the literature in air. The results show continuously decreasing SN curves under seawater conditions for all materials, with no detectable fatigue limit. Fracture surface investigations reveal large corrosion areas for the structural steel with, generally, no clear crack initiation location. The duplex stainless steel shows less corrosion pits but a high degree of scatter of the SN data. For the high‐strength steel, multiple crack initiation locations were observed from the surface.

Distribution of sulfate‐reducing bacteria in the crevice and its effect on the initial corrosion behavior of 2205 stainless steel in artificial seawater

AbstractIn the present study, the distribution and vitality of the sulfate‐reducing bacteria (SRB) inside the crevice were characterized by scanning electron microscopy and confocal laser scanning microscopy. Potentiodynamic polarization curve tests and electrochemical impedance spectroscopy were used to evaluate the corrosion resistance. Furthermore, a starvation experiment was conducted by controlling nutrients to investigate the effects of the crevices on the transportation of nutrients and the vitality of the SRB. The results demonstrate that it was more difficult for the SRB to enter the crevice, resulting in an incomplete biofilm formed on the surface. In addition, the insufficient supply of nutrients was also the reason for the low vitality of the SRB inside the crevice. Based on these results, it was inferred that the incomplete biofilm inside the crevice acted as a micro‐galvanic, thus making the corrosion rate of 2205 stainless steel in the initial crevice corrosion much more serious than that in the open system.

Corrosion behavior of a new 25Cr-3Ni-7Mn-0.66 N duplex stainless steel in artificial seawater

Abstract A new duplex 25Cr-3Ni-7Mn-0.66 N alloy was prepared in a vacuum arc re-melting furnace and characterized by metallographic and EPMA methods. Its corrosion behavior was investigated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and a Mott-Schottky (M-S) analysis in artificial seawater at room temperature and compared with those of super and normal commercial duplex stainless steel (SDSS and DSS). No significant difference in the open circuit potentials and pitting potentials was observed. Its passive film current density lies between those of SDSS and DSS. This was confirmed by EIS analysis. A pit attack was observed on the δ-phase for all duplex samples, because the PREN16 of the δ-phase was lower than that of the γ-phase. From the Mott-Schottky analysis, the passive films were found to be composed of bi-layer structures, a p-type semiconductor inner layer, and a n-type semiconductor outer layer. The degree of defect as well as the effect of nitrogen in passive film layer are discussed with respect to the point defect model.

Passivation behavior of 316L stainless steel in artificial seawater: effects of pH and dissolved oxygen

PurposeThe purpose of this paper is to investigate the influence of the potential of hydrogen (pH) and dissolved oxygen in artificial seawater on the passivation behavior of 316L stainless steel.Design/methodology/approachThe corrosion behavior was studied by using electrochemical measurements such as electrochemical impedance spectroscopy and polarization curve. The passive films were characterized with X-ray photoelectron spectroscopy.FindingsThe polarization resistance of the passive film decreases as the pH value drops ascribed to the formation of much more point defects. The donor carrier concentration (ND) in the passive film formed in the deaerated condition is lower than that in aerated conditions. Nevertheless, this phenomenon is the opposite when the pH value is 1 due to the significant decrease of Fe oxides/hydroxides coupled with the stable content of Cr oxides/hydroxides species. In addition, the compositional variation of the passive film also leads to the changes of its semiconductor properties from N-type to bipolar type.Originality/valueThis paper shows the variation of polarization resistance, corrosion potential, passive film composition and semiconductor properties with the pH value and dissolved oxygen. The results can serve as references to the further study on crevice corrosion of 316L in seawater.

Consideration of Repassivation Process Based on the Measurement pH in Crevice and Metal Dissolution Rate of SUS304 Stainless Steel in Artificial Seawater

Consideration of Repassivation Process Based on the Measurement pH in Crevice and Metal Dissolution Rate of SUS304 Stainless Steel in Artificial Seawater

Interspecies interactions of Vibrio azureus and Jeotgalibacillus alkaliphilus on corrosion of duplex stainless steel

Investigations of multispecies biofilms and the relationships among these species are crucial for understanding the microbiologically influenced corrosion of metal alloys in actual environments. This study investigated the corrosion of 2205 duplex stainless steel by pure cultures of marine Vibrio azureus and Jeotgalibacillus alkaliphilus and their mixture using different electrochemical and surface analysis techniques. The results showed a significant enhancement of the growth rate and an increase in the biomass population of the biofilm in the presence of both bacteria. Microbial community analysis revealed a harsh competition between the two species. V. azureus benefitted from the competition between the two strains, grew faster, and dominated in the biofilm. Electrochemical results showed an increase in both the anodic dissolution and cathodic oxygen reduction rates of the duplex stainless steel in artificial seawater containing the bacterial mixture. The electrochemical behavior was similar in the presence the bacterial mixture and V. azureus alone, confirming that this bacterium acted as a dominant competitor. AFM images showed larger pits with irregular shapes in the presence of both bacteria, indicating faster pitting propagation.

Relationship Between The Initiation Site Properties and Propagation Behavior in Early Stage of Crevice Corrosion for SUS304 Stainless Steel in Artificial Seawater

Relationship Between The Initiation Site Properties and Propagation Behavior in Early Stage of Crevice Corrosion for SUS304 Stainless Steel in Artificial Seawater

Early stage of marine biofilm formation on duplex stainless steel.

The aim of this work was to investigate the bacteria-surface interactions occurring during the first hour of adhesion of marine Pseudoalteromonas NCIMB 2021 at the surface of 2304 lean duplex stainless steel in artificial seawater. A complete characterization of the biofilm and the passive film was performed coupling epifluorescence microscopy, scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), and time of flight secondary ion mass spectrometry (ToF-SIMS). The coupling of XPS and ToF-SIMS analyses revealed that (1) protein and polysaccharide contents in the biofilm are similar in the presence or absence of nutrients, (2) the biofilm is mainly composed of proteins and the protein content is similar to the one of Tightly Bound EPS, (3) increased bacterial activity due to nutrients leads to chromium enrichment in the passive film in close vicinity to the bacteria.

Tribocorrosion behaviors of thermal spraying WC/Ni60 coated 316L stainless steel in artificial seawater

PurposeThis paper aims to improve the tribocorrosion properties of 316L, thus WC/Ni60 coated 316L was prepared by thermal spraying technique.Design/methodology/approachComposition and microstructure of WC/Ni60 coating was investigated, and tribological properties of 316 L and WC/Ni60 coating were studied under dry sliding, deionized water and artificial seawater.FindingsThe results showed that WC/Ni60 coating was lamellar structure, and the phase composition consisted of γ-Ni solid solution, carbides and borides. Furthermore, the hardness and corrosion resistance of 316 L in static seawater and wear resistance in dry sliding were improved by WC reinforced nickel-based coating. Furthermore, tribocorrosion results demonstrated that wear resistance of WC/Ni60 coating was also significantly better than 316 L, especially for higher load at artificial seawater. The reason can be attributed to the fact that the passive film of WC/Ni60 coating consisted of tungsten carbide, Ni(OH)2 and FeOOH for WC/Ni60 coating and only FeOOH for 316 L.Originality/valueAccording to this study, it can be concluded that WC phases acted as a role in resisting the wear damages. Meanwhile, Ni-based materials performed well in corrosion resistance. Thus, the combined-effect Ni-based alloys and WC phases in WC/Ni60 coating showed better tribocorrosion performance than 316 L.

Passivation behavior and surface chemistry of 2507 super duplex stainless steel in artificial seawater: Influence of dissolved oxygen and pH

Passivation and film chemistry of 2507 super duplex stainless steel in modified artificial seawater (ASW) are investigated. Removal of dissolved oxygen decreases the electric field strength and point defect diffusivity of the passive film. Passive current density in acidified ASW is higher than that in aerated ASW due to increased potential drop across film/solution interface, donor density and point defect diffusivity. The content of oxidized Cr, Fe(II) and hydroxides increases and film thickness reduces with acidification. In acidified ASW, passive film become denser from pre-passivation to passivation region and pores form accompanied with the increase of oxidized Fe after transpassivation.

Tribocorrosion Behavior of SAF 2205 Duplex Stainless Steel in Artificial Seawater

Tribocorrosion behaviors of SAF 2205 duplex stainless steel sliding against an Al2O3 counterpart were investigated in artificial seawater. The tribocorrosion mechanisms and synergistic actions between corrosion and wear were analyzed in this work. The results indicated that a higher load was beneficial for the formation of the σ intermetallic phase and strain hardening; thus, the hardness increased first, and then the pure mechanical wear resistance of SAF 2205 was improved by the hardening effect. The wear mechanisms of SAF 2205 were dominated by abrasive wear under lower loads and by abrasive wear and plastic deformation under higher loads. Furthermore, galvanic corrosion was established between the σ intermetallic phase/ferritic/austenitic and passive film (cathode)/fresh surface, which caused corrosion-accelerated wear. Thus, the total damage to SAF 2205 during tribocorrosion in artificial seawater was determined by the mechanical wear and synergetic effects between corrosion and wear. Therefore, improving hardness was an effective way to increase the tribocorrosion properties of metal materials, such as SAF 2205 and 316L.

Defined hydrodynamic shear stresses influence the adhesion behaviors of marine Bacillus sp. on stainless steel in artificial seawater

Formation of microbial biofilm on marine structures is crucial for subsequent attachment of macro fouling species and understanding the impact of fluid conditions on formation and growth of the biofilm is essential for preventing biofouling. Here we report the effect of shear stresses generated by laminar and weakly turbulent flow on the adhesion of typical marine bacterium Bacillus sp. biofilm on stainless steel. Numerical simulation was carried out to calculate the distribution of pressure and shear stress applied on adhered bacteria. The shear stress was proportional to both the distance from the center of rotating disk and rotation speed. The stress reached 18 Pa as the flow velocity was 2.4 m/s and the rotation speed was 600 rpm. Further adhesion testing revealed that development of the bacterial biofilm in early stage was unaffected by the shear stresses. However, shear stress regulated the adherence orientations of the bacteria on the steel surface. Turbulent flow obviously shaped development of the architecture of the biofilm, as revealed by CLSM and SEM characterization. Biofilm growth patterns were clearly observed under weakly turbulent flow, however, they were not seen under laminar flow. The microcolonies assumed elongated forms, possibly triggered by exerted pressure drag force. The results give insights into possibly controlling the formation of marine biofilm on marine infrastructures for desired antifouling performances.

Electrochemical recycling of cell phone Li-ion batteries: application as corrosion protector of AISI 430 stainless steel in artificial seawater

This article aims to present a new alternative to waste management of spent Li-ion batteries from cell phones. In this sense, the proposed is recycling the cobalt from Li-ion cathode by electrodeposition and apply it as corrosion protector of AISI 430 stainless steel. Thus, two greatest environmental problems can be solved, producing a low-cost and high-corrosion-resistant stainless steel. The cobalt electrodeposition bath came from acid dissolution of spent Li-ion cathode with chemical formula LiCoO2. The charge efficiency for cobalt electrodeposition in −1.0 V and pH = 3 reaches 95 %. A protective layer of Co3O4 was successfully obtained by treatment of AISI 430 stainless steel with cobalt electrodeposited at 800 °C for 200 h in air atmosphere. The corrosion current of AISI 430 stainless steel in artificial seawater was reduced from 30 to 0.76 μA cm−2. The treatment proposed produces a AISI 430 stainless steel with double of corrosion resistance and half of cost if compared with AISI 304 stainless steel.

The tribocorrosion behaviors of Hastelloy C276 alloy in seawater

Purpose – The aim of this work is to study the tribocorrosion behaviors of Hastelloy C276 alloy sliding against AISI 316 stainless steel in artificial seawater and distilled water. Design/methodology/approach – The electrochemical behaviors of Hastelloy C276 alloy are measured by potentiodynamic polarization method. The tribocorrosion properties are evaluated using an MRH-03 type ring-on-block test rig in artificial seawater with different salinity. The wear loss is determined by the difference of sample weight before and after tribocorrosion tests. Findings – The results show that the typical passivation behavior is observed for C276 alloy in seawater. The Hastelloy C276 alloy has the maximum corrosion current density in 3 percent seawater, which is the synergism of salt concentration and dissolved oxygen in seawater. Friction coefficients are in general larger in distilled water compared with seawater. The wear loss in seawater is always higher than that in distilled water for both alloys. Seawater could reduce the friction coefficient and the wear resistance. Originality/value – Many scientists focused on studying the friction behavior of passive metals sliding against alumina or zirconia, which was considered to act as inert antagonist in the experiments. However, there are few papers available on the tribocorrosion properties of passive metals sliding each other in corrosion mediums.

Electrochemical scaling of stainless steel in artificial seawater: Role of experimental conditions on CaCO3 and Mg(OH)2 formation

In seawater, during the application of cathodic protection, a scale layer forms on the metal surface. As function of its chemical composition and compactness, it can improve the metal protection against corrosion by reducing the oxygen diffusion. The present investigation focuses on the electrochemical scaling of stainless steel in artificial seawater. Formed scales were characterized by X-ray diffraction, Raman spectroscopy and scanning electron microscopy. It was found that the formed scales are mainly CaCO3 aragonite. The brucite (Mg(OH)2) was identified, as a component of the scale layer, only for a high temperature and a more cathodic potential. It was also shown that, unlike other substrates, stainless steel promotes the precipitation of brucite. If the experimental conditions favoured its formation, the scaling process starts with brucite deposition. The growth of CaCO3 nucleuses, developed on interstice, recovers after brucite layer.

Tribocorrosion behaviors of Ti–6Al–4V and Monel K500 alloys sliding against 316 stainless steel in artificial seawater

The tribocorrosion behaviors of Ti–6Al–4V and Monel K500 alloys sliding against 316 stainless steel were investigated using a ring-on-block test rig in both artificial seawater and distilled water. It is found that friction coefficients are in general larger in distilled water compared with seawater. The wear losses of Ti–6Al–4V and Monel K500 alloys are larger in seawater compared with distilled water. The mechanical action can destroy the passive film and increase the corrosion rate. The synergism effect between corrosion and wear occurs. The synergism action between corrosion and wear is related to the corrosion rate and with the increase of corrosion rate, the synergism becomes more important. 316 stainless steel suffers severe wear sliding against Monel K500 alloy compared with sliding against Ti–6Al–4V alloy in both distilled water and seawater.

A study of the galvanic corrosion of titanium/L 316 stainless steel in artificial seawater using electrochemical noise (EN) measurements and electrochemical impedance spectroscopy (EIS)

PurposeThis paper aims to investigate the galvanic corrosion of titanium/L 316 stainless steel, by electrochemical noise (EN), electrochemical impedance spectroscopy (EIS), and anode/cathode area ratio effect on the galvanic behavior of the couple.Design/methodology/approachThe EN measurement was employed to examine effects of anode to cathode area ratio on the galvanic corrosion behavior between stainless steel L 316 and titanium in artificial seawater. Current noise and potential noise were monitored simultaneously using a three‐electrode configuration under open‐circuit condition. The noise resistance was evaluated as the ratio of the standard deviation of the potential to that of the current noise after removing the DC component. The time‐series noise patterns were transformed into frequency domain by fast Fourier transformation and then their power spectrum densities (PSDs) at specified frequency were determined and compared with the EIS and polarization results.FindingsThe EN, EIS and polarization results were in agreement. Galvanic corrosion density increase and galvanic potential moved slowly to negative direction with decrease in anode/cathode area ratio. The results showed that the slope of PSD of the current (i.e the “roll off”) was rising slowly where the anode/cathode area ratio was declined. The relationship between polarization resistance (Rp) and noise resistance (Rn) was investigated. Rt was determined by EIS for samples, and its value compared with Rp and Rn. The result indicates that galvanic corrosion has an inversely relation with anode/cathode area ratio that exposed to aggressive environment.Originality/valueThis paper presents the application of noise analysis to demonstrate galvanic corrosion and the effect of area ratio anode/cathode on current density and galvanic potential.

An experimental study of crevice corrosion behaviour of 316L stainless steel in artificial seawater

The effects of applied torque on corrosion behaviour of 316L stainless steel with crevices were investigated using the cyclic potentiodynamic polarization method. Three kinds of crevices (316L-to-polytetrafluoroethylene, 316L-to-fluoroelastomeric and 316L-to-316L) were tested in artificial seawater at 50 °C. Corroded surface morphology was also investigated using scanning electron microscopy. Results indicate similar trends in crevice corrosion susceptibility with increasing applied torque. Among the three crevices, the 316L stainless steel specimen, coupled to the 316L stainless steel crevice former, is the most susceptible to crevice corrosion.

Fretting corrosion of a nitrogen-bearing austenitic stainless steel in artificial seawater and 0.1 M H 2SO 4

Armco Nitronic 60 (trademark of Armco Inc.) austenitic stainless, supplied in 76.2-mm-diameter annealed round bar, was tested for fretting behavior in its “as-received” and “solution heat treated” conditions. In the “as-received” condition, the microstructure showed a profusion of precipitates (nitrides, carbides, and carbonitrides), in the main, confined to grain boundaries. Solution heat treatment reduced the precipitate concentration but did not eliminate the second phase entirely. Fretting was carried out both in artificial seawater and 0.1 M H 2SO 4 to show the comparative effects of solution type. In artificial seawater, the form of scars in both “as-received” and “solution heat-treated” conditions, and the friction behavior, were broadly similar, reflecting the influence of solid precipitates, forming from the electrolyte outside the scar, becoming compacted back into the scar as fretting proceeds. In 0.1 M H 2SO 4, the absence of solid precipitate outside, and the continuous disruption of a passive oxide film inside the scar, gives rise to a different form of corrosion, i.e., severe crystallographic etching and intergranular attack. Friction results are unique under these conditions. Solution heat treatment only marginally improved the condition.