Simulated Anode Environment Research Articles

Electrochemical study on the effect of hydrogen on the passive film of selective laser melted 316L stainless steel in a proton exchange membrane water electrolyzer environment

The effect of hydrogen on the passivation behavior and electrochemical characteristics of selective laser melted (SLMed) 316L stainless steel in a simulated anode environment for a proton exchange membrane water electrolyzer (PEMWE) was studied. The results indicate that hydrogen charged into the sample increased the ratio of superficial Fe2+/Fe3+ and OH−/O2−, increased the concentration of point defects, reduced the film thickness, and weakened its protective effect. The film near 0.6 VSCE showed n-type semiconductor behavior. Hydrogen charging resulted in a higher defect density and thinner space charge layer in the film, which promoted the invasion of aggressive ions.

Corrosion-resistant, electrically conductive TiCN coatings for direct methanol fuel cell

To improve the resistance to corrosion attack, hydrophobicity and the electrical conductivity of stainless steel (SS) bipolar plates for usage in direct methanol fuel cells (DMFC), a TiCN nanostructured coating, with the average thickness about 15 μm, was deposited onto a 316L SS substrate using the double cathode glow discharge plasma (DCGDP) method. Electrochemical measurements were carried out at 50 °C to determine the corrosion performance of both bare and TiCN-coated 316L SS in a simulated anode environment, replicating the operating conditions of a DMFC, with different methanol concentrations (0.05 M H2SO4 + 2 ppm HF + x M methanol (where x = 5, 10, 15, 20)). The results showed that the electrochemical degradation rate of both materials decreased with increasing methanol addition due to the restriction of proton mobility in the solution through the action of the methanol. At all the methanol concentrations of the test solutions, the TiCN coating had higher corrosion potentials and lower corrosion current densities than bare 316L SS, thus showing better corrosion resistance and enhanced electrochemical stability. Moreover, interfacial contact resistance (ICR) measurements revealed that the TiCN coating immersed in all test solutions with different methanol concentrations maintained a very low ICR value, which was advantageous to the operation of DMFC. Therefore, the TiCN coating, combining excellent corrosion resistance with good electrical conductivity, is considered to be an attractive candidate to serve as a protective surface for SS bipolar plates.

Performance of Nb0.8Zr0.2 Layer-Modified AISI430 Stainless Steel as Bipolar Plates for Direct Formic Acid Fuel Cells

To improve the interfacial conductivity and corrosion resistance of AISI430 stainless steel (430SS) as bipolar plates for direct formic acid fuel cells (DFAFCs), a Nb0.8Zr0.2 layer has been successfully synthesized via the pulsed laser deposition (PLD) technique on the surface of 430SS. This Nb0.8Zr0.2 layer is smooth, uniform, and comparatively compact without any surface flaw and micropore. Investigation under the simulated anodic environment of DFAFCs (0.05 M H2SO4 + 2 ppm HF + 10 M HCOOH at 70 °C) shows that the corrosion resistance of 430SS is obviously ameliorated after the PLD modification. In addition, the interfacial contact resistance of Nb0.8Zr0.2-430SS (6.0 mΩ cm2) is much smaller than that of bare 430SS (151.3 mΩ cm2) at the clamping force of 140 N cm−2. Besides, different from the highly increased interfacial contact resistance of bare 430SS, the Nb0.8Zr0.2-430SS shows a minor increase resistance after potentiostatic tests in simulated anodic environment of DFAFCs.

Electrodeposited Ni–Mo–Cr–P coatings for AISI 1020 steel bipolar plates

Metallic bipolar plates (BPPs) are potential candidates to replace the conventional graphite BPPs in polymer electrolyte membrane fuel cells (PEMFCs) because they are cost-effective and easy to manufacture. In this present work, we report on the development of Ni–Mo–Cr–P electroplated AISI 1020 steel bipolar plates as a BPP material. The microstructure and composition of the Ni–Mo–Cr–P coatings were optimized varying pH of the electrolyte bath and deposition current. Compared to bare AISI 1020 steel, the coating electroplated at pH 5.5 and a pulse-current density of 0.075 A/cm2 showed an improvement in corrosion resistance by three orders of magnitude. The corrosion current densities of bare and Ni–Mo–Cr–P electroplated AISI 1020 steel in the simulated anodic environment is 1.05 × 10−2 and 4.95 × 10−5 A/cm2, respectively, while that in the simulated cathodic environment it is 3.7 × 10−2 and 4.58 × 10−5 A/cm2, respectively. The enhancement of corrosion resistance is due to the formation of a Mo and Cr based passive oxide layer. The interfacial contact resistance (ICR) of bare and Ni–Mo–Cr–P electroplated AISI 1020 steel is 53.2 and 40.06 mΩ, respectively. ICR of Ni–Mo–Cr–P is lower than the bare AISI 1020 because of the semiconducting nature of the two-layered Mo-based passive oxides. Additionally, Ni–Mo–Cr–P coated AISI 1020 steel shows a higher water contact angle than bare AISI 1020 carbon steel. A single-cell PEMFC stack with Ni–Mo–Cr–P coated AISI 1020 steel BPP shows similar polarization behavior as graphite BPP. However, the performance of Ni–Mo–Cr–P coated AISI 1020 steel BPP lacks durability, and further improvement is necessary before it can be commercially implemented.

Electrochemical properties of niobium and niobium compounds modified AISI430 stainless steel as bipolar plates for DFAFC

ABSTRACTThe highly conductive and corrosion resistant diffusion layers of niobium, niobium nitrides and niobium carbides have been successfully fabricated on AISI430 stainless steel (430 SS) via a plasma surface diffusion alloying (PSDA) method as bipolar plates for direct formic acid fuel cells (DFAFCs). The surface of niobium carbides modified 430 SS (NbC 430 SS) is relative densification and uniformity without other surface flaw and micropore. Potentiodynamic and potentiostatic polarisation measurements indicate that NbC 430 SS enhances the corrosion resistance more effectively than other modified samples and its corrosion current density is maintained approximately 2.5 μA cm–2 in the simulated anodic environment of DFAFC. Moreover, NbC 430 SS presents a superior hydrophobicity with a contact angle of 105.5° and a lower interfacial contact resistance (ICR) before and after potentiostatic polarisation tests than other specimens. Therefore, NbC 430 SS developed in this work has a great potential to be bipolar plates for DFAFCs.

Effect of diffusion alloying time on corrosion resistance and surface conductivity of niobium-alloying-modified AISI430 stainless steel for DFAFC bipolar plate

Purpose The purpose of this study is to improve the surface electrical conductivity and corrosion resistance of AISI430 stainless steel (430 SS) as bipolar plates for direct formic acid fuel cell (DFAFC). Design/methodology/approach The niobium diffusion layers have been successfully synthesized on 430 SS substrate by the plasma surface diffusion alloying technique under different diffusion alloying time. Findings The surface morphology of Nb-modified 430 SS prepared under the diffusion alloying time of 2 h is more homogeneous, relatively sleek and compact without surface micropore and other common surface blemishes. The potentiostatic and potentiodynamic polarization measurements manifest that Nb-modified 430 SS prepared under the diffusion alloying time of 2 h enormously ameliorate the corrosion resistance of bare 430 SS compared with other Nb-modified 430 SS samples and its corrosion current density is maintained at −1.4 µA cm−2 in simulated anodic environment of DFAFC (0.05 M H2SO4 + 2 ppm HF + 10 M formic acid at 50 °C). Originality/value The effect of diffusion alloying time on the corrosion resistance and surface conductivity of Nb-modified 430 SS has been carefully studied. The Nb-modified 430 SS samples prepared at the diffusion alloying time of 2 h have the best surface electrical conductivity and corrosion resistance in the simulated anodic environment of DFAFC.

Studies on the physical and electrochemical properties of Ni-P coating on commercial aluminum as bipolar plate in PEMFC

AA6061 samples were coated with electroless Ni-P after a pretreatment which consisted of either single, double or triple zincating. It was observed that increasing the number of zincating reduces the amount of zinc on the surface, and this has a direct effect on the initial rate of deposition of the Ni-P coating, which was confirmed through pH measurements. The corrosion performance of uncoated and coated AA6061 was evaluated at open circuit conditions with conventional electrochemical techniques in 0.5 M H2SO4 solution bubbled with H2 or O2 to simulate the anodic and cathodic environments respectively of a Proton Exchange Membrane Fuel Cell (PEMFC). In both environments the corrosion rate was lower in the presence of Ni-P coating compared to uncoated AA6061 and it also decreased while increasing the zincate pretreatment steps. This latter effect was attributed to higher P content and amorphous nature of the coating. Furthermore, it was observed that for all coated samples the corrosion rate was higher in the simulated cathodic environment. Potentiostatic tests were also carried out to further discuss the stability of the coatings and the results showed that the measured current density followed the same trend as the corrosion current density. It decreased with increasing number of zincate steps in both environments. Also, measured currents were lower in the simulated anodic environment, confirming a better stability in the anodic side.

Bipolar plate development with additive manufacturing and protective coating for durable and high-efficiency hydrogen production

Additive manufacturing (AM) of the complex devices for energy application remains an almost unexplored area, and the harsh acidic environment also limits the application of AM parts in water splitting for hydrogen production. Here, bipolar plates (BPs), which are used to transport reactants/products and conduct electrons in proton exchange membrane electrolyzer cells (PEMECs), are printed from stainless steel (SS) with selective laser melting (SLM). Then surface treatments are employed on those BPs by thin film electroplating with Au, and the protective thin layer enables the utilization of AM SS parts to both cathode and anode sides of water electrolyzer cells and exhibits superior corrosion resistances and electronic conductivities. The Au-coated AM SS BPs deliver a low interfacial contact resistance (6.4 mΩ cm2 under 1.45 MPa) and an excellent performance in PEMECs (1.71 V at 2 A/cm2), and maintain a remarkable durability in the simulated anode environment compared with the uncoated AM SS BPs and conventional graphite BPs. This approach demonstrates the possibility of 3-dimensional printing fully integrated water electrolyzer cells at both anode and cathode sides.

Corrosion and Electrical Properties of SS316L Materials in the Simulated HT-PEFC Environment

Increasing attention is being paid to the use of metallic materials as a replacement for non-porous graphite in the bipolar plates of polymer membrane fuel cells, including high-temperature polymer membrane fuel cells (HT-PEFCs). This work investigates the corrosion and electrical properties of SS316L stainless steel in the simulated anode and cathode environments of HT-PEFCs. The influence of gases on the free corrosion potential (Ecorr), free corrosion current (icorr) and dynamic formation of passive layers were analyzed in 85 wt% phosphoric acid at RT and 130°C by means of potentiodynamic and potentiostatic tests, together with open circuit potential (OCP) measurements. The working potential of the anode (0.05V) is located in the active corrosion region, while the working potential of the cathode (0.65V) is located in the passive corrosion region. The potentiostatic tests show that the corrosion rate of SS316L in the simulated anode environment of an HT-PEFC is 10 times higher than that in the simulated cathode environment of an HT-PEFC. The free corrosion potentials, immediately noted after potentiostatic tests, show that the existence of oxygen could improve the stability of the passive layer formed during the potentiostatic stage. Scanning electron microscopy (SEM) results showed different morphologies of the corroded surface. Inductively-coupled plasma optical emission spectrometry (ICP-OES) and interfacial contact resistance (ICR) was then used to determine the levels of metal ions in the solution after corrosion and the influence of the passive layer on the ICR of metallic bipolar-plates separately made from SS316L. X-ray photoelectron spectroscopy (XPS) was used to investigate the distribution of elements on the surface of samples before and after the corrosion tests. These ex-situ measurements showed that in the anode environment, SS316L undergoes active corrosion, which results in a higher level of leaching metal ions and lower value of ICR compared to that in a cathode environment, which has a passive corrosion environment. The specimen in the cathode environment showed lower values of ICR and the number of leaching metal ions when exposed to oxygen compared with the nitrogen atmosphere. The passive layer formed in a simulated cathode environment with an oxygen purge shows the best corrosion resistance within hot phosphoric acid. The XPS results indicate that this is a Cr-rich layer. The thickness of the surface films was estimated to range from 1.1–2.2 nm.

Performance of niobium nitride-modified AISI316L stainless steel as bipolar plates for direct formic acid fuel cells

A niobium nitride diffusion layer (Nb–N layer) has been synthesized via the plasma surface diffusion alloying (PSDA) technique on the surface of AISI316L stainless steel (316L SS), which is used as bipolar plates of direct formic acid fuel cells (DFAFCs). The niobium nitride-modified AISI316L stainless steel (Nb–N 316L SS) has a compact and successive niobium nitride diffusion layer with a single cubic NbN phase. The corrosion resistance and surface conductivity of Nb–N 316L SS are systematically investigated in the simulated anodic environments of DFAFC (0.05 M H2SO4 + 2 ppm HF + x M formic acid (x = 2, 5, 10 and 15) at 50 °C). The potentiodynamic and potentiostatic polarization tests demonstrate that the corrosion resistance of 316L SS is distinctly ameliorated in the simulated DFAFC environments after the PSDA modification. The interfacial contact resistances (ICR) of Nb–N 316L SS are much smaller than those of bare 316L SS before and after potentiostatic polarization tests.

Oxidation behaviour and phase transformations of an interconnect material in simulated anode environment of intermediate temperature solid oxide fuel cells

The oxidation behaviour and the phase transformations associated with high temperature exposure of a commercial ferritic interconnect steel, Crofer 22 H, was studied in a simulated solid oxide fuel cell (SOFC) anode atmosphere at 700 °C. Special emphasis was placed on the formation of the intermetallic sigma phase. No sigma phase was detected in the bulk alloy after 500 h of exposure of bare specimens. However, specimens which were pre-coated with a layer of nickel showed formation of an interdiffusion zone after as little as 2 h of exposure and sigma phase formation occurred after 10 h. The presence of the nickel layer, which simulates the contact between ferritic steel interconnects and a nickel mesh in a SOFC results in the formation of an austenitic zone and accelerated formation of a σ-phase rich layer at the ferrite/austenite interface. The ferritic steel is transformed into austenite due to the inward diffusion of nickel, σ-phase started to nucleate at the transformed austenite grain boundaries. The nucleation is enhanced by an increased Cr/Fe-ratio at that interface due to more pronounced diffusion of Fe, compared to Cr, in the direction of the Ni-layer. Different possible mechanisms for the nucleation and growth of σ-phase were identified. The experimental results led to the conclusion that sigma nucleates in the austenite and grows following an isothermal eutectoid-like decomposition. The kinetics of σ-phase formation and the depth of the interdiffusion zone were found to follow a traditional diffusion relationship. It was observed that as the Ni-concentration increases the sigma-phase re-dissolves and thus the zone which, contains sigma phase moves deeper into the ferritic steel with exposure time. Interdiffusion processes between the nickel layer and the ferritic steel result not only in accelerated formation of σ-phase but also in the formation of Cr-rich oxides within the nickel layer.

Niobium diffusion modified austenitic stainless steel bipolar plate for direct methanol fuel cell

An austenitic stainless steel with a niobium diffusion protective layer is evaluated for bipolar plate of direct methanol fuel cell (DMFC). Corrosion resistance of niobium diffusion modified AISI 304 stainless steel (niobized 304 SS) is investigated in simulated DMFC cathodic environment (0.5 M H2SO4 + 2 ppm HF + 0.1 M methanol solution at 50 °C) and anodic environment (0.5 M H2SO4 + 2 ppm HF + (1 M, 10 M and 20 M) methanol solution at 50 °C), respectively. Potentiodynamic, potentiostatic as well as electrochemical impedance spectroscopy tests show that, comparing with a bare 304 SS, the corrosion current density of niobized 304 SS is reduced greatly while the polarization resistance is raised in the simulated DMFC cathodic environment. Corrosion tests in the simulated anodic environment are applied to examine the effect of methanol on the corrosion behaviour of niobized 304 SS. It is interesting to find that the niobized 304 SS shows better corrosion resistance in the higher methanol concentration solutions.

Conductive amorphous carbon-coated 316L stainless steel as bipolar plates in polymer electrolyte membrane fuel cells

Amorphous carbon (a-C) film about 3 μm in thickness is coated on 316L stainless steel by close field unbalanced magnetron sputter ion plating (CFUBMSIP). The AFM and Raman results reveal that the a-C coating is dense and compact with a small size of graphitic crystallite and large number of disordered band. Interfacial contact resistance (ICR) results show that the surface conductivity of the bare SS316L is significantly increased by the a-C coating, with values of 8.3–5.2 mΩ cm 2 under 120–210 N/cm 2 . The corrosion potential ( E corr ) shifts from about −0.3 V vs SCE to about 0.2 V vs SCE in both the simulated anode and cathode environments. The passivation current density is reduced from 11.26 to 3.56 μA/cm 2 with the aid of the a-C coating in the simulated cathode environment. The a-C coated SS316L is cathodically protected in the simulated anode environment thereby exhibiting a stable and lower current density compared to the uncoated one in the simulated anode environment as demonstrated by the potentiostatic results.

An investigation into the effects of a nano-thick gold interlayer on polypyrrole coatings on 316L stainless steel for the bipolar plates of PEM fuel cells

Polypyrrole is one of the most important conductive polymers because it is easily oxidized, water soluble and commercially available. Also, polypyrrole coatings have potential applications in batteries, fuel cells, electrochemical sensors, anti-corrosion coatings and drug delivery systems. In this study, a very thin gold layer was first coated on SS316L, and then a polypyrrole coating was laid on top. The nucleation and growth mechanisms of polypyrrole on the gold-coated SS316L were studied by electrochemical nucleation and growth techniques. SEM was used to characterize the polypyrrole coating morphology. Potentiodynamic tests were performed to determine the corrosion parameters of the polypyrrole coatings. Potentiostatic tests of the coated SS316L were conducted in simulated anode and cathode environments of a PEM fuel cell. The simulated anode environment was at a potential of about −0.1 V versus SCE purged with H 2 and the simulated cathode environment was at a potential of about 0.6 V versus SCE purged with O 2. After coating with Au and polypyrrole, the polarization resistance of SS316L is increased about six times, and the corrosion current density is decreased about seven times, compared to the base SS316L. Also, our calculations show that the metal ion concentration in solution for the polypyrrole/Au/SS316L had met the target of 10 ppm after 5000 h fuel cell operation.

Effects of O2 and H2 on the corrosion of SS316L metallic bipolar plate materials in simulated anode and cathode environments of PEM fuel cells

Abstract Increasing attention is being paid to the use of metallic materials as a replacement for non-porous graphite in bipolar plates (BPs) for polymer exchange membrane (PEM) fuel cells. The main aim of the present study was to investigate how O2 and H2 affect the corrosion behavior of 316L stainless steel in simulated anode and cathode environments of a PEM fuel cell. Open circuit potential (OCP) measurements together with potentiodynamic and potentiostatic tests were performed to investigate the corrosion behavior of SS316L in the O2- and H2-containing environments. Optical microscopy and scanning electron microscopy (SEM) were used to characterize the morphology of the corroded surface and the corrosion products. Inductively coupled plasma optical emission spectrometer (ICP-OES) was used to determine the levels of metal ions in solution after corrosion. The OCP and potentiodynamic tests showed that less corrosion of SS316L took place in a simulated cathode environment because it was easier to passivate SS316L in an O2-containing environment. However, the potentiostatic tests showed that there is less corrosion in a simulated anode environment, because H+ ions are reduced, and the resulting negative current can provide partial cathodic protection to the SS316L.

An investigation of the electrochemical properties of PVD TiN-coated SS410 in simulated PEM fuel cell environments

Bipolar plates are a key component of PEM fuel cells, and they constitute a large portion of the weight and total cost of a fuel cell stack. In order to reduce both the cost and weight of the bipolar plates, considerable attention is being paid to developing metallic bipolar plates to replace non-porous graphite. In this study, TiN was coated on a martensitic stainless steel (SS410) using a PVD technology (plasma enhanced reactive evaporation) to increase the corrosion resistance of the base metal. XRD, SEM, EIS and potentiodynamic tests were used to characterize the TiN-coated SS410. In order to investigate the suitability of these coated materials as the anodes and cathodes in a PEMFC, potentiostatic tests were conducted under both simulated cathode and anode conditions. The simulated anode environment was - 0.1 V vs SCE purged with H 2 and the simulated cathode environment was 0.6 V vs SCE purged with O 2 . The dense TiN coatings formed on SS410 much improved the corrosion resistance of SS410 and, thus, these coated materials could potentially be used in PEMFCs as a bipolar plate material provided they also satisfy the other physical and mechanical property requirements such as interfacial contact resistance, light weight, high mechanical strength and manufacturability.

An investigation into TiN-coated 316L stainless steel as a bipolar plate material for PEM fuel cells

In order to reduce the cost, weight and volume of the bipolar plates, considerable attention is being paid to developing metallic bipolar plates to replace the non-porous graphite bipolar plates that are in current use. However, metals are prone to corrosion in the proton exchange membrane (PEM) fuel cell environments, which decreases the ionic conductivity of the membrane and lowers the overall performance of the fuel cells. In this study, TiN was coated on SS316L using a physical vapor deposition (PVD) technology (plasma enhanced reactive evaporation) to increase the corrosion resistance of the base SS316L. X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical methods were used to characterize the TiN-coated SS316L. XRD showed that the TiN coating had a face-centered-cubic (fcc) structure. Potentiodynamic tests and electrochemical impedance tests showed that the corrosion resistance of SS316L was significantly increased in 0.5 M H 2SO 4 at 70 °C by coating with TiN. In order to investigate the suitability of these coated materials as cathodes and anodes in a PEMFC, potentiostatic tests were conducted under both simulated cathode and anode conditions. The simulated anode environment was −0.1 V versus SCE purged with H 2 and the simulated cathode environment was 0.6 V versus SCE purged with O 2. In the simulated anode conditions, the corrosion current of TiN-coated SS316L is −4 × 10 −5 A cm −2, which is lower than that of the uncoated SS316L (about −1 × 10 −6 A cm −2). In the simulated cathode conditions, the corrosion current of TiN-coated SS316L is increased to 2.5 × 10 −5 A cm −2, which is higher than that of the uncoated SS316L (about 5 × 10 −6 A cm −2). This is because pitting corrosion had taken place on the TiN-coated specimen.

Investigation on Haynes 242 Alloy as SOFC Interconnect in Simulated Anode Environment

The oxidation behavior of Haynes 242 alloy was studied at 700-900°C in Ar + 4 vol % H 2 + 3 vol % H 2 O which corresponds to the solid oxide fuel cell (SOFC) anode environment. The oxidation kinetics was found to obey a parabolic law and the oxidation activation energy (181.5 kJ mol -1 ) was close to that for the self-diffusion of the Cr cation in Cr 2 O 3 , indicating that the oxidation process was mainly controlled by outward diffusion of the Cr cation in Cr 2 O 3 . The oxide scale was composed mainly of Cr 2 O 3 with a thin (Mn,Cr) 3 O 4 spinel top layer. The area specific resistance of the oxide scale formed in the reducing atmosphere was found to be higher than that formed in air.

05/02069 A non-interior point approach to optimum power flow solution

A niobium nitride diffusion layer (Nb–N layer) has been synthesized via the plasma surface diffusion alloying (PSDA) technique on the surface of AISI316L stainless steel (316L SS), which is used as bipolar plates of direct formic acid fuel cells (DFAFCs). The niobium nitride-modified AISI316L stainless steel (Nb–N 316L SS) has a compact and successive niobium nitride diffusion layer with a single cubic NbN phase. The corrosion resistance and surface conductivity of Nb–N 316L SS are systematically investigated in the simulated anodic environments of DFAFC (0.05 M H2SO4 + 2 ppm HF + x M formic acid (x = 2, 5, 10 and 15) at 50 °C). The potentiodynamic and potentiostatic polarization tests demonstrate that the corrosion resistance of 316L SS is distinctly ameliorated in the simulated DFAFC environments after the PSDA modification. The interfacial contact resistances (ICR) of Nb–N 316L SS are much smaller than those of bare 316L SS before and after potentiostatic polarization tests.

Corrosion behavior of TiN coated type 316 stainless steel in simulated PEMFC environments

The corrosion behavior of TiN coated type 316 stainless steel (SS) was investigated in simulated proton exchange membrane fuel cell environments, i.e. 0.01 M HCl + 0.01 M Na 2SO 4 solutions bubbled with pure oxygen and hydrogen gases, respectively, by using electrochemical measurement techniques. 316SS substrate can passivate spontaneously in simulated cathode environment, while it is in active state at the corrosion potential in simulated anode environment. TiN coatings have much better corrosion resistance and passivity under both simulated conditions. No significant degradation takes place in TiN coatings under the typical load conditions of fuel cell for 4 h. The loss of small part of coatings occurs during the immersion tests of TiN coatings in the oxygen environment for 1000 h and in the hydrogen environment for 240 h, respectively, but the exposed substrate areas are passivated in both environments. The results reveal that TiN coating can offer 316SS higher corrosion resistance and electric conductivity, and that further effort to improve the coating quality and to evaluate the long-term stability of 316SS/TiN coating systems under simulated conditions are deserved. In addition, the characteristics of corrosion process for TiN coatings on passivatable substrate were discussed in detail.