Enhancing the localised corrosion resistance of 316L stainless steel via FBR-CVD chromising treatment

Localized corrosion of stainless steels by chloride ions in seawater leads to metal degradation while fouling of marine organisms increases the occurrence of localized corrosion. We describe a simple method to increase hydrophobicity of austenitic stainless steel using grain boundary etching that can also inhibit adhesion of bio-organisms present in seawater as well as increase the localized corrosion resistance of stainless steel in chloride-containing aqueous environments. This paper describes the corrosion behavior of stainless steel as a result of grain boundary etching to achieve hydrophobicity. Potentiostatic polarization on stainless steel 316L in a nitric acid solution at an anodic potential of 1.3 V vs. saturated calomel electrode (SCE) results in a grain boundary etched structure and a Cr- and Mo-rich passive film as confirmed by scanning electron microscopy and X-ray photoelectron spectroscopy. This modified stainless steel 316L surface exhibits enhanced corrosion resistance to a 0.6 M sodium chloride solution. Specifically, potentiodynamic polarization studies indicate that the breakdown potential increases and the sample-to-sample variability decreases. The modified surfaces show a narrow range of breakdown potentials (0.96 to 1.05 V vs. SCE) compared to as-received stainless steel 316L (0.32 to 0.86 V vs. SCE).

Case hardening by traditional carburization or nitridation methods has long been recognized to produce wear resistant surfaces in steels. When these methods are applied to stainless steels, corrosion performance is degraded because of carbide and nitride formation. However, low temperature gas-phase and plasma interstitial hardening (IH) processes relying on paraequilibrium kinetics have been developed (1-5) that allow substantial amounts of carbon or nitrogen to be introduced into stainless steels without formation of carbides or nitrides. Paraequilibrium refers to the concept that diffusion kinetics of substitutional solutes, such as Cr and Ni, diffuse slower than interstitial solutes, such as carbon or nitrogen. Substitutional solutes are effectively immobile, whereas interstitial solutes can diffuse into the alloy to depths of 10-30 µm. Surface carbon or nitrogen concentrations on the order of 12 at% or greater can be obtained, resulting in a hardened surface. This modified case-hardened region has been referred to as S-phase or expanded austenite. The industrial implementation of the IH treatment with carbon (IH-C) or nitrogen (IH-N) is straightforward, is a non-line of sight process, maintains sample dimensions, and is relatively inexpensive. A growing body of work on IH-C treated stainless steel alloys shows that gas phase IH-C treatment improved localized corrosion, fatigue, and wear resistance of the treated materials compared to the untreated alloys (5-9).The origin of the hardening and the improved corrosion resistance for IH-C treated 316L stainless steels is the “colossal” supersaturation of interstitial carbon. The corrosion resistance of stainless steel involves a Cr2O3-rich passive film. In previous work, grazing incidence X-ray photoelectron spectroscopy (GI-XPS) was used to determine the composition and measure the thickness of these Cr-rich passive films developed during anodic polarization at selected potentials for both IH-C and non-treated 316L stainless steel samples. Since no Cl-was observed in the passive oxide film of both the IH-C and non-treated samples at any of the potentials examined, and the chemical composition was the same for IH-C and non-treated samples at each potential, we suggest that passive film breakdown is of chemo-mechanical origin [8,9].In this work, exploration into the nature of passive oxide film breakdown was extended to gas phase IH-N. The experimental work conducted follows that of IH-C in References 7 and 9. This includes determining the polarization behavior in 0.6 M NaCl solutions, performing potentiostatic experiments at selected potentials below the pitting potential with subsequent XPS, and impedance measurements on the electronic response of the oxide film. XPS will be used to determine the oxide film thickness and composition of the potentiostatically polarized samples. These results will then be compared to the results reported in References 7 and 9. Acknowledgements The authors gratefully acknowledge the Office of Naval Research and the Naval Research Laboratory for financial support of this work. References (1) Z.L. Zhang and T. Bell, Surf. Eng., 1,131 (1985).(2) P.C. Williams and S.C. Marx: U.S. Patent 6,093,303, July 25, 2000.(3) Y. Cao, F. Ernst, and G.M. Michal, Acta Mater., 51, 4171 (2003).(4) T. Christiansen and M.A.J. Somers, Surf. Eng., 21,445 (2005).(5) G.M. Michal, F. Ernst, H. Kahn, Y. Cao, F. Oba, N. Agarwal, and A.H. Heuer, Acta Mater., 54, 1597 (2006).(6) A.H. Heuer, H. Kahn, J. O'Donnell, G.M. Michal, R.J. Rayne, F.J. Martin, and P.M. Natishan, Electrochem. and Solid State Lett., 13 (12) C37-C39 (2010).(7) F.J. Martin, E.J. Lemieux, T.M. Newbauer, R.A. Bayles, P.M. Natishan, H. Kahn, G.M. Michal, F. Ernst, and A.H. Heuer, Electrochem. and Solid State Lett., 10 (12) C76-C78 (2007).(8) A.H. Heuer, H. Kahn, P.M. Natishan, F.J. Martin, and L.E. Cross, Electrochimica Acta, 58,157 (2011). (9) A.H. Heuer, H. Kahn, F. Ernst, G.M. Michal, D. Hovis, R.J. Rayne, F.J. Martin, and P.M. Natishan, Acta Materialia, 60, 716 (2012).

Effect of surface nanocrystallization induced by fast multiple rotation rolling on hardness and corrosion behavior of 316L stainless steel

Improving the electrochemical corrosion behavior of stainless steel (316L) through the deposition of tantalum-based thin films

Optimization of electrochemical corrosion behavior of 316L stainless steel as an effective biomaterial for orthopedic applications

Stainless steel substrates of exhaust mufflers made of aluminized stainless steel can be exposed to solutions containing Al3+ ions long after the dissolution of their Al coating. This study examined the corrosion behavior of stainless steel in synthetic condensed water that contained different amounts of Al dissolution. The corrosion resistance of stainless steel in the solution containing dissolved Al3+ ions decreased. The unstable passive film contained Al oxides (or hydroxides), which decreased the protective properties of the stainless steel. The dissolved Al3+ ions in the exhaust condensed solution had a negative effect on the corrosion resistance of the stainless steel.

ABSTRACTAs an alloying element, molybdenum has a positive impact on the localized corrosion resistance of stainless steels and Ni‐based alloys. Nevertheless, the impact of minor changes from 0.5 to 1.0 wt% within the composition boundaries of SS316L on localized corrosion resistance is poorly understood. This study investigates the influence of these variations on the localized corrosion resistance of SS316L. Using the potentiodynamic–galvanostatic–potentiodynamic (PD–GS–PD) technique, the crevice corrosion repassivation potential (ER,CREV) was measured in deaerated natural seawater at various temperatures for three stainless steel grades with differing Mo contents. The ER,CREV of SS316‐2.5Mo increased by approximately 125 mV at 10°C, 139 mV at 20°C, and 218 mV at 35°C when compared to SS316‐2Mo. Microstructure analysis after PD–GS–PD revealed Mo‐enriched precipitates for both SS316‐2.5Mo and SS317‐3Mo. Potentiodynamic polarization test was conducted in pit/crevice‐like conditions, showed improved corrosion resistance in SS316‐2.5Mo, as indicated by higher breakdown and Flade potentials, a wider passive range, particularly in 1 M [Cl−] (pH = 0).

The effect of surface enriched chromium and grain refinement by ball milling on corrosion resistance of 316L stainless steel

The studies on the corrosion behaviors of 316NG and 304NG nitrogen-containing stainless steels made in China

Stainless steel is widely used in marine environments due to its excellent corrosion resistance properties. However, recent occurrences of corrosion issues related to Type 316L stainless steel in marine atmospheric environments have led to concerns regarding the suitability of Type 316L stainless steel material selection according to international standards. Factors such as surface roughness and passivation treatments can significantly affect the corrosion behavior of stainless steel in marine atmospheres. In particular, the surface roughness of conventional stainless steel piping can lead to corrosion in marine atmospheric environments when exposed for extended periods. Either option requires improving the surface roughness or applying passivation treatments to enhance corrosion resistance.This study examines the effect of surface roughness on the corrosion resistance of Type 316L stainless steel in a marine environment using potentiodynamic polarization and accelerated corrosion tests. In addition, the impact of organic acid passivation on the corrosion behavior of stainless steel in a marine atmosphere is investigated. Surface roughness was controlled by mechanical polishing, while organic acid passivation was achieved using a solution containing citric acid, phosphoric acid, and hydrogen peroxide. Electrochemical measurements and surface characterization techniques were employed to assess the corrosion resistance of the specimens. The results demonstrate that surface roughness and organic acid passivation significantly impact the corrosion resistance of stainless steel in a marine atmosphere. Understanding the synergistic effects of these factors is crucial for enhancing the durability and performance of stainless steel components in marine applications.

The changes in the inclusions in 316L stainless steel before and after Ce addition were studied by adding different contents of Ce. The effects of rare earth Ce treatment on the modification of MnS inclusions in steel and the pitting corrosion resistance of 316L stainless steel are studied by field-emission scanning electron microscopy, laser confocal microscopy, the 6% FeCl3 corrosion weight loss test, and Tafel polarization curve test. The results show that the addition of Ce reduces the corrosion rate of stainless steel in 6% FeCl3 solution, and reduces the number and size of corrosion pits. The corrosion resistance is the best at a 0.0082% Ce content. In addition, the addition of Ce reduced the corrosion current density of stainless steel in 3.5% NaCl solution and increased the corrosion potential. The corrosion potential increased from -329 mV to -31.4 mV. Through Ce treatment, the grain is refined and the inclusions in the experimental steel are modified. With the increase in rare earth content, Mn S gradually transforms into Ce2O2 S inclusions. The morphology of the inclusions gradually change from the original long strips to a spherical shape, and the average size is significantly reduced, which improves the corrosion resistance of the stainless steel. The addition of rare earth Ce plays modifies the inclusions and purifies molten steel.

Galvanic Corrosion Behavior of Copper and Stainless Steel in Heat Exchanger Environments

An investigation of the electrolytic solution effects on stainless steel electrode for dye-sensitized solar cells

The goal of this study was to investigate the pitting corrosion resistance of AISI 316L (UNS S31603) stainless steel in Ringer’s solution after electrochemical polishing of the samples in a magnetic field induced by a permanent magnet under varying induction. For the studies, the complete statistical program of investigation was adopted on the basis of the five-level compositive rotary plan. The analysis of the results obtained in this work shows that the magnetic field considerably affects the corrosion resistance of austenitic stainless steel of Type AISI 316L electropolished under varied conditions. The magnetic field introduced during electropolishing has a big influence on the pitting corrosion resistance of stainless steels. A mathematical model has been found to be an exponential regression formula Upit = f (i, B), where Upit (mV) is the pitting potential, i (A/dm2) is the current density, and B (mT) is the magnetic induction.

The purpose of this research is to investigate cold work effect on corrosion behavior of stainless steels of type AISI 304, AISI 316L and AISI 2101. The specimen were processed through cold work simulated by the tensile test at various percentages elongation and then tempered at 600°C for different time intervals. Two electrochemical techniques and hardness test were utilized in this investigation. The first technique was the double loop electrochemical potentiokinetic reactivation (DL-EPR) that yields the values of degrees of sensitization (DOS). The second one was the cyclic potentiodynamic polarization (CPP) to study the ability of the metals to build or repair the damaged films under localized corrosion. The DOS values from the DL-EPR tests of the samples under the same heating conditions suggested that specimens drawn at higher percentage elongation tend to have more chromium depleted areas. Also, the test specimens with more exposure time to heat were more prone to chromium deficiencies. As for the ability of the metal to create or repair damaged film after corrosion has occurred, it was found that AISI 316L had hihger corrosion resistance than AISI 304. However, AISI 2101 stainless steel had highest corrosion resistance. In this study, it was also found that AISI 2101 did not exhibit pitting corrosion, but the crevice corrosion. This could be due the fact that AISI 2101 which is a duplex stainless steel has high corrosion resistance and could trigger the crevice corrosion take place before the pitting initiation.