Passivated Stainless Steel Research Articles

Effects of nitric acid passivation on the corrosion behavior of ZG06Cr13Ni4Mo stainless steel in simulated marine atmosphere

AbstractZG06Cr13Ni4Mo martensitic stainless steel was nitric acid‐passivated to improve its corrosion performance. The effects of nitric acid passivation on the surface morphology, chemical composition, electrochemical properties, semiconductor behavior, and long‐term corrosion performance of the stainless steel were investigated using various analytical techniques. An in‐depth analysis of X‐ray photoelectron spectroscopy (XPS) showed that the passive film formed after the acid passivation process showed high thickness and a duplex character as it consisted of a hydroxide layer and an oxide layer. The oxide layer affected the corrosion resistance and thickness of the passive film. The thickness of the passive film was calculated theoretically as well as experimentally by fitting the electrochemical impedance spectroscopy and XPS results. The electrochemical tests revealed that the dramatic increase in the corrosion resistance of the stainless steel after the passivation was due to the formation of a thick, low‐disorder passive film rather than Cr enrichment. The removal of inclusions resulted in higher pitting resistance, whereas the increased roughness showed a negative effect on the corrosion behavior of the stainless steel. During the wet–dry cyclic tests, the modification of the passive film was examined. The passivated stainless steel exhibited good corrosion resistance for up to 50 days of exposure in the simulated environment.

Longevity Aspects of Potable Water Disinfected by Ionic Silver: Kinetic Experiments and Modeling

In the International Space Station (ISS), Russian and European cosmonauts drink water disinfected by dissolved silver. For this to be effective, the concentration of silver should remain above a certain threshold from the moment of its initial disposition in storage tanks on earth until its final consumption in ISS. Unfortunately, during water tanks transportation to ISS and during storage in ISS, silver concentration has been reported to decrease intensively beyond any reason. This work examines the effect of different materials used in ISS water storage and distribution systems on the reduction of silver concentration. An experimental campaign has been organized where passivated stainless steel (SS), passivated and electropolished SS and titanium alloy coupons (official ISS grades) are exposed to simulated ISS potable water at different silver concentrations, different surface to volume ratios, and at stagnant or flow conditions. The evolution of silver concentration remaining in the bulk water is recorded with respect to the exposure time. A reaction engineering model for the Ag loss to the coupons is developed. The model is fitted to the experimental data in order to derive the reaction rate expression and the corresponding parameters. For passivated SS and electropolished SS the silver deposition rate depends on the initial silver concentration in water but is rather unaffected by the progress of silver deposition on the surface. On the other hand, for Ti alloy, while silver deposition rate still depends on initial silver concentration, it decreases continuously as silver deposition on the surface advances, implying that Ti alloy surface becomes gradually saturated and so prevents further silver deposition. Such a model can be useful for material selection and design of water storage and distribution facilities for ISS.

Aging study of Gd concentration in LAB-based Gd loaded liquid scintillator exposed to passivated stainless steel

Stainless steel is a candidate of the inner surface of the storage container for LAB-based Gadolinium loaded liquid scintillator (Gd-LS) to be used in the JSNS2 neutrino detector. Aging effect on Gd concentration of Gd-LS was investigated with the Gd-LS sample stored in the passivated stainless steel bottle by two independent methods. The direct comparison of the neutron capture time measurement showed that there is no significant degradation of the capture time after 617 days aging. Titration was performed to measure Gd concentration, and the result after 466 days aging is consistent with the result before aging within the uncertainty of the measurement. Both results lead to a conclusion that stainless steel is usable for Gd-LS storage for JSNS2 experiment.

Synthesis and Evaluation of Anionic Schiff Bases As Pitting Corrosion Inhibitor for Stainless Steel 304 in NaCl Solution

The high corrosion resistance of austenitic stainless steel (SS) arises from the formation of a thin, adherent and protective passive film that forms instantaneously on the surface. Unfortunately, in the presence of aggressive ions like chloride anion, the corrosion resistance of passivated stainless steel is limited by local breakdown and pit nucleation [1]. An efficient and economical method to decrease the metal dissolution in aggressive media is the use of corrosion inhibitors. A large number of organic molecules containing electronegative functional groups, such as π-electron systems or heteroatoms have been proposed for the inhibition of general metallic corrosion, although the use of organic compounds as pitting corrosion inhibitors in neutral solutions is still rather limited. On the other hand, inorganic-based compounds such as chromates and nitrates are also used as pitting corrosion inhibitors for SS in aggressive media; however the application of these inorganics, especially chromates and phosphates, is not recommended because of their biological toxicity. More recently, Schiff bases have been described as cost effective inhibitors due to their robust and convenient synthesis from inexpensive precursors. They are organic compounds containing the imine (-C=N-) functional group in their structure. Schiff base derivatives with additional heteroatoms, such as N and O, and aryl groups have been used as corrosion inhibitors [2,3], but their application as pitting corrosion inhibitors has not been described. In the present study, three new anionic Schiff bases were synthesized through by reacting para-amino benzoic acid with several aromatic aldehydes containing different functional groups in their para- site. They were designed to improve water solubility, to enhance coordination with Fe atoms by including N and O heteroatoms, two benzene rings and the imine group in their chemical structure, and to be large enough to create heavy hydrophobic complex with Fe+3. The inhibitor efficiency of these compounds as pitting corrosion inhibitor for 304 SS in neutral 0.1 M NaCl was examined using potentiodynamic polarization measurements, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) . Polarization data show the shift of the pitting potential to more positive values with increasing inhibitor concentration. Surface analysis shows chromium enrichment at the metal surface under anodic polarization in the passive region of the metal when the inhibitor compound is present in the test solution, whereas no effect occurs under open circuit conditions. XPS data show that the inhibitor molecules do not adsorb on the clean metal, but on the passive layer instead. [1] G.T. Burstein, C. Liu, R.M. Souto, S.P. Vines, Corros. Eng. Sci. Technol. 39 (2004) 25. [2] M.A. Hegazy, Corros. Sci. 51 (2009) 2610. [3] R. Sadeghi Erami, M. Amirnasr, K. Raeissi, M.M. Momeni, S. Meghdadi, J. Iran. Chem. Soc. 12 (2015) 2185.

Evaluation of interaction between Sn and passivated stainless steel through an easy chromaticity approach

The interaction between Sn and passivated stainless steel was evaluated through an easy chromaticity approach. The microstructure of Fe–Sn intermetallics (IMCs) was observed, and their growth was inspected at different time after the interaction. The oxide film on stainless steel exposed in air locally delayed IMC growth, and the chemically passivated film protected stainless steel from Fe–Sn compound formation. To investigate the interaction mechanism, the integrity of passivated films grown on stainless steel was evaluated by chromogenic inspection. The interaction extent was related to colour measurement a*. Results indicated that the measured value of a* from the inspection decreased with the increasing exposure time, and a minimum a* value was found in chemically passivated samples. The tendency of the colour measurement was consistent with the effect of passive film on IMC growth. The interfacial reaction of passivated stainless steel with Sn was illustrated based on the integrity of the passive films.

Devising the Specification of a Solar Cell Utilizing TiO2 Photoanode and Copper Oxides Photocathode

We have been studied the performance of Marine Microbial Fuel Cell (MMFC) composed of Titanium dioxide anode and marine microbial film cathode. In order to improve the power density of MMFC, we have studied to improve the photocatalytic effects of TiO2 anode such as the effect of impurities on TiO2, double layer coating of TiO2, the effect of heat treatment on TiO2, and the effect of dye sensitizing on TiO2. On the other hand, the photocathodic effect of Copper oxides cathode has been studied such as the effect of heat treatment on Copper oxides. Based on the photocatalytic semiconductor effects of TiO2 and Copper oxides, we tried to develop a solar cell coupled with TiO2 photoanode and Copper oxides photocathode. The base metal used for both electrodes was Type 329J4L stainless steel substrate. The surface cleaning and passivation treatment were performed to the substrate before coating of photoactive layers. To produce TiO2 electrode, the passivated substrate was coated with TiO2 first layer by screen printing method followed by 150 °C heat treatment for 60 minutes. The second layer of TiO2 was coated by screen printing and heat treatment was performed at 550 °C for 30 minutes. Besides, vacuum deposition method was used to the base substrate to produce Copper oxides cathode. A set of copper wires was evaporated and deposited on the substrate in vacuum evaporator. The copper-deposited substrate was then heat treated at 350 °C for 30 minutes to form Copper oxides film on the substrate. To compare the characteristics of electrodes, the passivated stainless steel was used as a cathode in couple with TiO2 electrode in the measurements. The electrolyte used for the measurement was artificial sea water (Aquamarine). The cell voltage measurement and power density measurement was performed by a potentiostat (Syrinx, SDPS- 501C, 511C). Two types of cell was prepared; TiO2 anode vs Copper oxides cathode cell and TiO2 anode vs passivated stainless steel cathode cell. Firstly, the measurement of cell voltage for these cells were performed under light irradiation. The light used for these experiments was a xenon lamp with 150 W and calibrated wavelength range of 250 nm to 800 nm which produced a light intensity of 10.5 mW/cm2 (equivalent to approximately 1/10th of 1 sun) onto the test electrode. From the results of cell voltage measurement, power density measurement of the cell was performed in dark condition and under irradiated condition from open circuit cell voltage to short circuit cell voltage. The current densities at which the maximum power density from these cells was obtained and at at which the linear portion of the graph (Tafel gradient) was obtained were recorded for AC impedance measurement as the EIS analysis. The AC impedance measurement of these cells were performed at the current density points obtained from above under irradiated and dark conditions. As the EIS analysis, the Cole-Cole plot and the Bode plot was obtained, and the equivalent circuit was constructed. The results from these experiments were compared and analysed. The results showed the open circuit cell voltage and maximum current density and hence maximum power density of the cell using TiO2 anode and Copper oxides cathode under light irradiation was increased compared to the cell without irradiation. This showed the photocatalytic effect of Copper oxides and Titanium dioxide. The performance of the cell with TiO2 anode vs Copper oxides cathode was increased compared to that of the cell with TiO2 anode and Stainless steel cathode. This is due to increased photocatalytic effect of copper oxide by vacuum deposition. By comparing AC impedance measurement results, the capacitive component of the impedance was reduced largely in the cell with TiO2-Copper oxides than TiO2-stainless steel cell. This leaded to a decrease of cell internal resistance by introducing Copper oxides cathode.

Evolution of unpredictable behaviour of a passivated stainless steel measured electrochemically

We report here the very slow activation of a stainless steel measured by long-term constant-potential polarisation in acidic solution in a region where the net current is cathodic. This unexpected and unpredictable behaviour follows a period of time in which the metal appears to demonstrate an increasing state of passivity. The activation is observed as an increase in the cathodic current density arising from surface accumulation of electrocatalytic components, which accompanies the slow dissolution of the metal. The activation process takes a significant period of time to manifest itself, and then evolves very slowly: it does not reach a steady state even after several days of polarisation at constant potential. These unique observations introduce potential difficulties involved in long-term prediction of corrosion behaviour using short-term electrochemical measurements.

Development of an In Situ Thermal Desorption Gas Chromatography Instrument for Quantifying Atmospheric Semi-Volatile Organic Compounds

Semi-volatile organic compounds (SVOCs) play a significant role in the formation of secondary organic aerosol, but their atmospheric abundance and chemical composition are poorly understood. We have developed a new system for the thermal desorption aerosol gas chromatograph (TAG) that extends its capability to quantitatively speciate SVOCs (semi-volatile TAG) having vapor pressures lower than tetradecane (C14) with hourly time resolution. The key component is a passivated stainless steel fiber filter that quantitatively collects both gas and particle phase organic compounds. A separation between gas and particle phase collection is determined through a difference method by periodically sampling ambient air through a multichannel charcoal denuder that efficiently removes gas-phase compounds. Measurements made with this new instrument will provide constraints on the abundance, chemical composition, and gas-to-particle partitioning of atmospheric SVOCs and provide opportunities to improve our understanding of secondary organic aerosol formation in the atmosphere. Copyright 2013 American Association for Aerosol Research

Effect of Passivation Treatments on the Corrosion Resistance of PIM 316L Stainless Steel in a PEM Fuel Cell Simulated Environment

In this work, the corrosion resistance of passivated PIM 316L stainless steel specimens was evaluated in 1M H2SO4 + 2 ppm HF solution at room temperature during 28 days of immersion. Passivation was carried out in HNO3and H2SO4solutions. The electrochemical behavior of the passivated specimens was assessed through electrochemical impedance spectroscopy and anodic polarization curves. Scanning electron microscopy (SEM) was employed to observe the surface of the specimens before and after the passivation treatments. The results pointed to a strong influence of the passivation conditions on the corrosion resistance of the specimens.

Module to guide the expert use of x-ray photoelectron spectroscopy by corrosion scientists

This contribution, to the potential development of data systems having some degree of “expert” character for use in x-ray photoelectron spectroscopy (XPS), illustrates the manner in which models of “Rules” might be developed by the user community. The field of corrosion science is taken as an example of one community of researchers who make regular use of XPS for well defined needs. These “needs” are redefined as a series of Goals that have to be reached in order to characterize the surface in terms of layer sequences and the enrichment of given elements within them. Rules are written to allow a structured approach to achieve each Goal. A feature of this set of Rules is that they are designed expressly to allow automated interpretation of the survey scan. This approach is facilitated by the use of a recommendation that the survey spectrum be acquired as a series of accumulated scans instead of the usual approach of making a single scan through the spectrum. Repeat scans enable the information extracted by the operation of the Rules to be processed and displayed for information during the period that is normally used for the survey scan. It is intended that this information will inform the setting up of any subsequent high resolution scans and their interactive interpretation. It will also inform any future operations such as ion etching or angle-resolved measurements. In some cases, the information made available may be all that is required by the user and in this case the “expert module” approach becomes particularly cost effective. The operation of the rules is illustrated throughout by an examination of data obtained for passivated stainless steel, giving a data set of measurements, typical of those made by corrosion scientists, that can be compared with the literature values obtained by more conventional XPS interpretation.

The observation of the early stages of pitting on passivated type 304 stainless steel in a 0.5 M NaCl solution at low potentials in the passive region by using the AC impedance method

The changes of electrochemical parameters on the passivated electrode of type 304 stainless steel in a 0.5 M NaCl solution at different low potentials ranging from − 250 to − 100 mV (SCE) in the passive region are studied using the AC impedance method. It is found that the electrode reaction is under metal charge-transfer control at potentials below 200 mV, and the charge-transfer resistance decreases with increasing potential. It is possible that pit nucleation occurs on the passivated stainless steel at this stage. When the potential is above − 200 mV, because of the diffusion process appearing in Bode impedance plots, both the metal charge-transfer and diffusion processes occur on the electrode. The metal charge-transfer resistance decreases and the diffusion coefficient increases with increasing potential. The nucleated pits on passivated stainless steel proceed to the stage of metastable growth at the potentials above − 200 mV. This potential of − 200 mV can be estimated as the level at which metastable pits start to grow on passivated type 304 stainless steel.

Evaluation of canisters for measuring emissions of volatile organic air pollutants from hazardous waste incineration.

Regulation to control air emissions of toxic organic compounds require the collection and analysis of effluent gas from low level sources such as hazardous waste incinerators. The standard SW-846 Method specifies the use of Tenax and Tenax/charcoal adsorbent traps for collection of volatile organics from incinerators. This study evaluates passivated stainless steel canisters as an alternative to adsorbent traps to eliminate some of the problems associated with adsorbent sampling. Initially the stability of 18 nonpolar, volatile organic compounds was determined in Summa-treated stainless steel canisters with greater than 100 ppmv HCl and saturated with water vapor. All 18 components were stable for a two-week period; however, an interference caused a 10-fold increase in the FID response of trichloroethylene, toluene, and chlorobenzene. No interference of the ECD response was found for any of the 11 compounds detected with the ECD including trichloroethylene. A pilot scale incinerator was sampled using canisters, and the destruction efficiency of 1,1,1-trichloroethane was determined at a concentration of less than 0.5 ppbv while determining 1,1-dichloroethylene, the major product of incomplete combustion, at a concentration of 8000 ppbv from the same sample.