316L SS Surface Research Articles

Surface and Protein Adsorption Properties of 316L Stainless Steel Modified with Polycaprolactone Film.

The surface and protein adsorption properties of 316L stainless steel (316L SS) modified with polycaprolactone (PCL) films are systematically investigated. The wettability of the PCL films was comparable to that of bare 316L SS because the rough surface morphology of the PCL films counteracts their hydrophobicity. Surface modification with PCL film significantly improves the corrosion resistance of the 316L SS because PCL is insulating in nature. A coating of PCL film effectively reduces the amount of adhered bovine serum albumin (BSA) on the surface of 316L SS in a bicinchoninic acid protein assay. PCL is both biodegradable and biocompatible, suggesting the potential for the surface modification of implants used in human bodies; in these applications, excellent corrosion resistance and anticoagulant properties are necessary.

Galvanic deposition and characterization of brushite/hydroxyapatite coatings on 316L stainless steel

In this work, brushite and brushite/hydroxyapatite (BS, CaHPO4·H2O; HA, Ca10(PO4)6(OH)2) coatings were deposited on 316L stainless steel (316LSS) from a solution containing Ca(NO3)2·4H2O and NH4H2PO4 by a displacement reaction based on a galvanic contact, where zinc acts as sacrificial anode. Driving force for the cementation reaction arises from the difference in the electrochemical standard potentials of two different metallic materials (316LSS and Zn) immersed in an electrolyte, so forming a galvanic contact leading to the deposition of BS/HA on nobler metal. We found that temperature and deposition time affect coating features (morphology, structure, and composition). Deposits were characterized by means of several techniques. The morphology was investigated by scanning electron microscopy, the elemental composition was obtained by X-ray energy dispersive spectroscopy, whilst the structure was identified by Raman spectroscopy and X-ray diffraction. BS was deposited at all investigated temperatures covering the 316LSS surface. At low and moderate temperature, BS coatings were compact, uniform and with good crystalline degree. On BS layers, HA crystals were obtained at 50°C for all deposition times, while at 25°C, its presence was revealed only after long deposition time. Electrochemical studies show remarkable improvement in corrosion resistance.

Repassivation behavior of 316L stainless steel in borate buffer solution: Kinetics analysis of anodic dissolution and film formation

The repassivation behavior of metals or alloys after oxide film damage determines the development of local corrosion and corrosion resistance. In this work, the repassivation kinetics of 316L stainless steel (316L SS) are investigated in borate buffer solution (pH 9.1) by using the abrading electrode technique. The current densities flowing from bare 316L SS surface are measured by potentiostatic method and analyzed to characterize repassivation kinetics. The initial stages of current decay (t<500ms) are discussed according to a film growth model, which describes the initial current transient should be divided into substrate dissolution current and passive film formation current based on Avrami kinetics. Then the two independent components are analyzed individually. The film formation rate and the thickness of film are compared in different applied potential. It is shown that anodic dissolution dominates the repassivation for a short time during the early times, and a higher applied potential will promote the anodic dissolution of metal. The film growth rate increases slightly with increasing in potential. Correspondingly, increase in applied potential from 0VSCE to 0.8VSCE results in thicker monolayer, which covers the whole bare surface at the time of θ=1. The electric field strengths through the thin passive film could reach 3.97×106Vcm−1.

Cytocompatibility of Fe-O Thin Film Prepared by Unbalanced Magnetron Sputtering

In order to improve the cell biocompatibility of pure iron surface as cardio-vascular stent material, Fe-O film was deposited on single crystal silicon by unbalanced magnetron sputtering. Human umbilical vein endothelial cells were seeded on the 316L SS, pure iron and Fe-O film surface, whereafter cultured in vitro. Adhesion behavior was detected after 2 h incubation. Cell morphology and proliferation activities were assessed at 1, 3 and 5 days. The results show that the endothelial cells are easy to adhere and spread on the surface of Fe-O film. Compared with 316L SS samples, the cells count and area coverage of Fe-O film in 1 and 5 days make a difference significantly. These results demonstrated that the Fe-O film prepared by unbalanced magnetron sputtering technique has good cytocompatibility.

Oxazole derivatives as corrosion inhibitors for 316L stainless steel in sulfamic acid solutions

Oxazole derivatives were investigated as corrosion inhibitors for 316L stainless steel (SS) in sulfamic acid (NH2HSO3) solutions by potentiodynamic polarization, electrochemical impedance spectroscopy, and electrochemical frequency modulation techniques. The results showed the variation in inhibition performance of the inhibitors with varying concentrations and temperatures. The maximum efficiency was found to be 91% at 2 × 10−4 M concentration of the inhibitors for the immersion period of 3 h. Langmuir was tested to describe the adsorption behavior of inhibitor on 316LSS surface. Potentiodynamic polarization study clearly revealed that these compounds act as mixed-type inhibitors. The results of the electrochemical impedance study showed a decrease in double layer capacitance and increase in charge transfer resistance. The results of various electrochemical techniques show good agreements with each other.

Electrochemical polishing as a 316L stainless steel surface treatment method: Towards the improvement of biocompatibility

A 316L stainless steel (316L-SS) surface was electrochemically polished (EP) in an electrolyte of a new chemical composition at different cell voltages, with the aim of improving its corrosion resistance and biocompatibility. X-ray photoelectron spectroscopy results revealed that the EP-formed oxide films were characterized by a significantly higher atomic Cr/Fe ratio and film thickness, in comparison to the naturally-grown passive oxide film formed on the untreated (control) 316L-SS surface. As a result of the increase in the oxide film thickness and relative Cr enrichment, the EP-treated 316L-SS surfaces offered a notable improvement in general corrosion resistance and pitting potential. In addition, the attachment of endothelial cells (ECs) and smooth muscle cells (SMCs) to the 316L-SS surfaces revealed a positive effect of electropolishing on the preferential attachment of ECs, thus indicating that the EP surfaces could be endothelialized faster than the control (unmodified) 316L-SS surface. Furthermore, the EP surfaces showed a much lower degree of thrombogenicity in experiments with the platelet-rich plasma. Therefore, the use of the electrochemical polishing technique in treating a 316L-SS surface, under the conditions presented in this paper, indicates a significant improvement in the surface’s performance as an implant material.

The Crevice Corrosion of 316&amp;lt;i&amp;gt;L SS&amp;lt;/i&amp;gt; Alloy in NaCl Solution at Different Applied Potentials

316L SS alloy was tested under different applied potentials to study the susceptibility of this alloy to crevice corrosion. XPS measurements have been carried out to detect and define the products which formed on the surface of 316L SS in 3.5% NaCl at room temperature at applied potential = 200 mVSCE. The formation of Fe, Cr and Mo compounds were found, and these compounds play a great role in protecting the alloy which was found. The boundaries of the corroded area under washer teeth are in agreement with IR drop. The potentiodynamic technique is also studied to examine the overall corrosion behavior of 316L SS.

Investigation of corrosion behaviors at different solutions of boronized AISI 316L stainless steel

In this study, corrosion behaviors of boronized and non-boronized AISI 316L stainless steel (AISI 316L SS) were investigated with Tafel extrapolation and linear polarization methods in different solutions (1 mol dm−3 HCl, 1 mol dm−3 NaOH and 0.9% NaCl) and in different immersion times. AISI 316L SS were boronized by using pack boronizing method for 2 and 6 hours at 800 and 900°C within commercial Ekabor®-2 powder. Surface morphologies and phase analyses of boride layers on the surface of AISI 316L SS were characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis. SEM-EDS analyses show that boride layer on AISI 316L SS surface had a flat and smooth morphology. It was detected by XRD analyses that boride layer contained FeB, Fe2B, CrB, Cr2B, NiB and Ni2B phases. Boride layer thickness increases with increased boronizing temperature and time. The corrosion experiments show that boride layer significantly increased the corrosion resistance of the AISI 316L SS in 1 mol dm−3 HCl solution. While no positive effect of the boride layer was observed in the other solutions the corrosion resistance of the borid layer on AISI 316L SS was increased in all solution with the increase of the waiting periods.

Protectivity and Adhesive Strength of Zinclipscombite Coating on 316L Stainless Steel

Zinclipscombite (ZnFe3+2(PO4)2(OH)2) coating layer was prepared on 316L SS. The 316L SS plates were treated using hydrothermal treatment at 200°C for 2, 6 and 24 h. The ZnFe3+2(PO4)2(OH)2 layer strongly attached to the 316L SS surface. The adhesive strength of the coating layer was measured higher than 65.7 ± 3 MPa. The surface observation and element analysis indicated that the 316L SS plates were covered with ZnFe3+2(PO4)2(OH)2 coating layer after hydrothermal treatment. Linear voltammograms for treated sample at 200°C for 24 h showed higher corrosion resistance. The ICP results proved protective property for the zinclipscombite coating agains PBS solution.

Forming &lt;i&gt;In-Situ&lt;/i&gt; Micro-Cavities on 316L Stainless Steel Surface by Aluminum Electrodeposition and Anodization Technology

We have studied the anodization behavior of an Al film electrodeposited on the 316L stainless steel (316L SS) substrate and demonstrated an effective approach to fabricate the micro-cavities on the conducting substrate through anodic aluminum oxide (AAO) template. The morphologies and composition of the electroplating aluminum layers and the micro-cavities were evaluated by SEM and energy dispersive X-ray analysis (EDXA) respectively. The results indicated that different shapes of cavities with size ranging from 0.6 to 2 mm were come into being directly on 316L SS substrates. The size of cavities could be controlled by adjusting the anodizing voltage and time. And the morphologies of the initial aluminum films were found to be critical factors for successfully anodizing the Al film on 316L SS surface.

Investigation on Pitting Corrosion of Nickel-Free and Manganese-Alloyed High-Nitrogen Stainless Steels

Pitting corrosion behavior of three kinds of nickel-free and manganese-alloyed high-nitrogen (N) stainless steels (HNSSs) was investigated using electrochemical and immersion testing methods. Type 316L stainless steel (316L SS) was also included for comparison purpose. Both solution-annealed and sensitization-treated steels were examined. The solution-annealed HNSSs showed much better resistance to pitting corrosion than the 316L SS in both neutral and acidic sodium chloride solutions. The addition of molybdenum (Mo) had no further improvement on the pitting corrosion resistance of the solution-annealed HNSSs. The sensitization treatment resulted in significant degradation of the pitting corrosion resistance of the HNSSs, but not for the 316L SS. Typical large size of corrosion pits was observed on the surface of solution-annealed 316L SS, while small and dispersed corrosion pits on the surfaces of solution-annealed HNSSs. The sensitization-treated HNSSs suffered very severe pitting corrosion, accompanying the intergranular attack. The addition of Mo significantly improved the resistance of the sensitization-treated HNSSs to pitting corrosion, particularly in acidic solution. The good resistance of the solution-annealed HNSSs to pitting corrosion could be attributed to the passive film contributed by N, Cr, and Mo. The sensitization treatment degraded the passive film by decreasing anti-corrosion elements and Cr-bearing oxides in the passive film.

The electrochemical impedance of polarized 316L stainless steel: Structure‐property‐adsorption correlation

Electrochemical (EC) impedance and polarization data were synergistically coupled with AFM micrographs providing insight on the polarized alloy-electrolyte interface. Several regions of oxide topography/ impedance characteristic were apparent on a 316L SS surface. A relatively rough surface with apparent EC reaction products was observed below -500 mV. Smooth surfaces were seen from -500 mV to 200 mV. A transition region which displayed the aggregation of particles on the surface was seen from 200 mV to 600 mV. Above 600 mV these particles disappeared revealing a smooth topography. These topographical observations matched closely with the impedance behavior of the system, particularly the capacitance (C), polarization resistance (R(p)) and current density. The presence of pre-adsorbed Fb had a significant impact on C below approximately -500 mV (increased capacitance). The deviation from ideality of the current response as determined by a KWW empirical dielectric decay function showed significant differences between PBS-immersed and pre-adsorbed Fb cases. Earlier, changes in Fb area coverage, height, and eccentricity were observed between voltages lower and higher than 0 mV. The presence of the flat-band potential around -150 mV as well as high cathodic charge-transfer reactions taking place below -100 mV relate to these observations.

Interactions between stainless steel, shear stress, and monocytes

Angioplasty with stent placement is commonly used to treat coronary atherosclerosis. However, 20-40% of stainless steel stents restenose within 6 months via a prolonged inflammatory response mediated by monocytic infiltration and cytokine secretion. In the current study, we tested a hypothesis that blood flow and monocytes interact to alter stent corrosion. We assessed the effects of THP1 monocytes on the corrosion rate of 316L stainless steel (316LSS) under shear stress (0.5-50 dyn/cm(2)). In addition, THP1 cytokine secretion was determined using cytokine arrays and ELISA analyses. Data were compared using ANOVA and Tukey post hoc analysis (alpha = 0.05). Monocytes significantly lowered 316LSS corrosion rates without limiting current density. However, shear stress alone did not alter the corrosion rate of 316LSS. THP1 cells adhered to the 316LSS surface at all flow rates. Exposure to the 316LSS/corrosion test under high fluid flow rates increased (>twofold) the secretion of 7 of the 42 cytokines tested (angeogenin, GRO, I309, interleukin 8, interleukin 6, interleukin 1beta, and macrophage chemoattractant protein-1). Each of these cytokines play a role in wound healing, macrophage differentiation, and cell proliferation, all hallmarks of in-stent restenosis. Furthermore, only IL8 levels were significantly higher than any of the system controls during the 316LSS/corrosion test conditions. The IL8 levels from the 316LSS/corrosion tests were not significantly different from the +LPS control. Together, these data suggest that monocytic cells maybe activated by exposure to 316LSS stents and could contribute to in-stent restenosis and altered corrosion of the stent.

Immobilization of NaIO4‐treated heparin on PEG‐modified 316L SS surface for high anti‐thrombin‐III binding

Poor compatibility between blood and metallic coronary artery stents is one reason for arterial restenosis; however, the immobilization of anticoagulant agents on the surface of the stent is a feasible method of improving stent compatibility. Heparin, a well-known anticoagulant, has been frequently used to coat the surfaces of certain biomaterials to attain blood compatibility. The compound 1-ethyl-3-(3-dimethyl-aminopropyl) carbodiimide has often been utilized for the immobilization of heparin, but the critical carboxyl groups of heparin (with regards to heparin's anticoagulant activity) will be reduced by this method. This study examined possible methods of heparin immobilization without consuming these carboxyl groups. The 316L stainless steel surface was first activated with hexamethylene diisocyanate and then coupled with bis-amine-terminated poly (ethylene glycol) (BA-PEG) so as to create active amine groups. Sodium periodate (NaIO(4); SP) was then used to oxidize heparin to form aldehyde groups. The treated heparin could then be grafted onto the activated surface of the test material without losing its carboxyl groups. Effective surface modification of the hexamethylene diisocyanate-activated and BA-PEG-grafted 316L SS surface was confirmed using Fourier Transform Infrared Spectroscopy, electron spectroscopy for chemical analysis and a water contact angle test. After the heparin was immobilized on the BA-PEG-grafted 316L SS surface by SP, the surface showed an improvement in antithrombrin III (AT III) binding ability, its anticoagulant property, and hemocompatibility in comparison with heparin grafted by 1-ethyl-3-(3-dimethyl-aminopropyl) carbodiimide.

Pitting corrosion behavior of 316L stainless steel in the media of sulphate-reducing and iron-oxidizing bacteria

Pitting corrosion behavior of 316L SS was investigated in the presence of aerobic and anaerobic bacteria isolated from cooling water system in oil refinery using polarization measurement, electrochemical impedance spectroscopy, scanning electron microscopy examinations and energy dispersive spectrum analysis. The results show the corrosion potential ( E corr), pitting potential ( E pit) and polarization resistance ( R P) of 316L SS had a distinct decrease in the presence of bacteria, in comparison with those observed in the sterile medium for the same exposure time interval. Micrometer-scale pitting was observed on the 316L SS surface in the presence of bacteria. The combination of SRB and IOB demonstrated higher corrosion rates than SRB or IOB alone. The synergy of 0.01 M NaCl + SRB + IOB yielded the highest corrosion rate. The synergies between the metal surface, abiotic corrosion products, chloride anion, and bacterial cells and their metabolic products increased the corrosion damage degree of the passive film and accelerated pitting propagation.

Quantification of fibrinogen adsorption onto 316L stainless steel

Adsorption of the plasma protein fibrinogen (Fb) onto 316L stainless steel (316L SS) was observed and quantified using both in situ and ex situ atomic force microscopy techniques. Industry standard mechanical and electrochemical polishing techniques were used to prepare bulk alloy 316L SS samples, rendering the surfaces flat enough to directly observe and measure Fb adsorption. The data were analyzed kinetically using a Langmuir model. Largely irreversible adsorption was found on the 316L SS surface with an adsorption rate constant (k(o)) of 1.9 x 10(-4) mL microg(-1) s(-1) using the ex situ method and 1.7 x 10(-4) mL microg(-1) s(-1) using the in situ method. Additionally, protein conformation and assembly orientation on these surfaces were documented, where the adsorption pattern appeared random. Complete area coverage was never obtained. That is, after adsorption for over 5 time constants (5tau), voids in the structure were always observed.

Retention and Desorption of Discharge Gases in Wall Materials Used for Large Helical Device

In the Large Helical Device, the control of particle recycling is one of important issues. Glow discharge cleanings (GDC) have been conducted to control the particle recycling in LHD. In order to simulate such the particle behavior, the glow discharge apparatus was fabricated, and retention and desorption of hydrogen and helium GDC gases were examined for stainless steel liner and graphite sample. The retained amount of hydrogen was one or two orders of magnitude larger than that of helium in both the wall materials. The helium ion impact desorption was observed to be effective to reduce the hydrogen retention. On the other hand, hydrogen ion impact was ineffective to reduce the helium retention. It was also seen that the impurities at the top surface of 316L SS was removed during GDC for only several hours.