• Transactions of Materials Processing
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• v.8 no.3
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• pp.301-301
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• 1999

Austenitic stainless steels such as AISI 316L have been used in equipment in which fluid flows at high speeds which can induce cavitation erosion on metallic surfaces due to the collapse of cavities, where the collapse is caused by the sudden change of local pressure within the liquid. Usually AISI 316L is susceptible to cavitation erosion. This research focuses on developing a better material to replace the AISI 316L used in equipment with high speed fluid flow, such as impellers. The effects of Rare Earth Metal (REM) additions on the cavitation erosion-corrosion resistance of duplex stainless steels were studied using metallographic examination, the potentiodynamic anodic polarization test, the tensile test, the X-ray diffraction test and the ultrasonic cavitation erosion test. The experimental alloys were found to have superior mechanical properties due to interstitial solid solution strengthening, by adding high nitrogen (0,4%), as well as by the refinement of phases and grains induced by fine REM oxides and oxy-sulfides. Corrosion resistance decreases in a gentle gradient as the REM content increases. However, REM containing alloys show superior corrosion resistance compared with that of other commercial alloys (SAF 2507, AISI 316L). Owing to their excellent mechanical properties and corrosion resistance, the alloys containing REM have high cavitation erosion-corrosion resistance.

• Journal of the Korean institute of surface engineering
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• v.52 no.2
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• pp.96-102
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• 2019

Magnesium and its alloys are prone to be corroded, thus surface treatments improving corrosion resistance are always required for practical applications. As a surface treatment of magnesium alloys, plasma electrolytic oxidation (PEO), creating porous stable oxide layer by a high voltage discharge in electrolyte, enhances the corrosion resistance. However, due to superhydrophilicity of the porous oxide layer, which easily allow the penetration of corrosive media toward magnesium alloys substrate, post-treatments inhibiting the transfer of corrosive media in porous oxide layer are required. In this work, we employed a hydrophobizing method to enhance the corrosion resistance of PEO treated Mg alloy. Three types of hydrophobizing techniques were used for PEO layer. Thin Teflon coating with solvent evaporation, self-assembled monolayer (SAM) coating of octadecyltrichlorosilane (OTS) based on solution method and SAM coating of perfluorodecyltrichlorosilane (FDTS) based on vacuum method significantly enhances corrosion resistance of PEO treated Mg alloy with reducing the contact of water on the surface. In particular, the vacuum based FDTS coating on PEO layer shows the most effective hydrophobicity with the highest corrosion resistance.

• Corrosion Science and Technology
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• v.23 no.4
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• pp.266-277
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• 2024

Due to its good corrosion and heat resistance with excellent mechanical properties, 304L stainless steel is commonly used in the fabrication of spent nuclear fuel dry storage canisters. However, welds are sensitive to stress corrosion cracking (SCC) due to residual stress generation. Although SCC resistance can be improved by stress relieving the weld and changing the chloride environment, it is difficult to change corrosion environment for certain applications. Stress control in the weld can improve SCC resistance. Ultrasonic shot peening (USP) needs further research as compressive residual stresses and microstructure changes due to plastic deformation may play a role in improving SCC resistance. In this study, 304L stainless steel was welded to generate residual stresses and exposed to a chloride environment after USP treatment to improve SCC properties. Effects of USP on SCC resistance and crack growth of specimens with compressive residual stresses generated more than 1 mm from the surface were studied. In addition, correlations of compressive residual stress, grain size, intergranular corrosion properties, and pitting potential with crack propagation rate were determined and the improvement of SCC properties by USP was analyzed.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.216-221
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• 2001

The surface treatment technique to increase corrosion resistance is very important in mechanical components of structures. Therefore, this paper investigates the effects of shot peening on the corrosion resistance of SCM 420steel. The results show that the surface compressive residual stress largely increases, which cause the increase of corrosion resistance.

• International Journal of Ocean System Engineering
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• v.3 no.1
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• pp.33-37
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• 2013

Reinforced concrete structures have been increasingly widely used in numerous industrial fields. These structures are often exposed to severely corrosive environments such as seawater, contaminated water, acid rain, and the seashore. Thus, the corrosion problems that occur with the steel bars embedded in concrete are very important from the safety and economic points of view. In this study, the effects of the cover thickness on the corrosion properties of reinforced steel bars embedded in multiple mortar test specimens immersed in seawater for 5 years were investigated using electrochemical methods such as the corrosion potentials, polarization curves, cyclic voltammograms, galvanostat, and potentiostat. The corrosion potentials shifted in the noble direction, and the value of the AC impedance also exhibited a higher value with increasing cover thickness. Furthermore, the polarization resistance increased with increasing cover thickness, which means that the oxide film that is deposited on the surface of a steel bar surrounded by alkali environment exhibits better corrosion resistance because the water, chloride ions and dissolved oxygen have difficulty penerating to the surface of the steel bar with increasing cover thickness. Consequently, it is considered that the corrosion resistance of reinforced steel can be improved by increasing the cover thickness. However, the corrosion resistance values of a steel bar estimated by measuring the corrosion potential, impedance and polarization resistance were not in good agreement with its corrosion resistance obtained by polarization curves.

• Journal of Ocean Engineering and Technology
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• v.23 no.5
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• pp.85-91
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• 2009

A stainless steel that contains aggressive negative ion was known to decrease the corrosion resistance. Stainless steel with super corrosion resistance was developed for improvement of corrosion resistance. Super duplex stainless steel is widely used under sever environment because of good mechanical properties and corrosion resistance. Also, Super duplex stainless steel has long life in severe environments by showing the enough strength and corrosion resistance. But duplex stainless steel is not stabilized compared to austenite stainless steel in corrosion resistance. In this study, corrosion characteristic were investigated to super duplex stainless steel with additive 0.2% nitrogen with $SiO_2$ thin films coated or no coated by sol-gel method in 3.5% NaCl. From test results, corrosion current density in the heat-treated specimen for ${\sigma}$ phase precipitation was higher than that of different heat-treated specimen. Also, $SiO_2$ colloidal-coated specimen had not occurred almost corrosion.

• Journal of the Korean Society for Heat Treatment
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• v.29 no.4
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• pp.168-175
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• 2016

Influence of trace amount of Ca addition on the corrosion resistance was comparatively investigated in solutionized Mg-4%Zn and Mg-4%Zn-0.1%Ca alloys. In as-cast state, the alloys were characterized by primary ${\alpha}-(Mg)$ dendrite with MgZn intermetallic compound particles. After solution-treatment, both alloys consisted of single ${\alpha}-(Mg)$ phase by dissolution of the compound particles into the matrix. It was found from the immersion and electrochemical corrosion tests that the Mg-4%Zn alloy had better corrosion resistance than the Mg-4%Zn-0.1%Ca alloy. Morphological and compositional analyses on the surface corrosion products indicate that the incorporation of Ca oxide with low PBR value into the surface corrosion products would be responsible for the decreased corrosion resistance of the Ca-containing alloy.

• Journal of the Korean institute of surface engineering
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• v.57 no.3
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• pp.221-224
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• 2024

The 304 stainless steel has good corrosion resistance, so it is used in various industries. However, in an environment like seawater, stainless steel can be damaged by chloride ions, resulting in surface corrosion such as pitting and crevice corrosion. Electropolishing is a technique that smooths the surface and creates a passivation layer that can resist corrosion. In this study, electropolishing was applied as a surface finish to increase the smoothness of the metal surface and its corrosion resistance. We confirmed the topology of the electropolished surface of stainless steel by optical microscope and evaluated the corrosion resistance characteristics of electropolished stainless steel through a potentiodynamic experiment.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.28 no.2
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• pp.208-215
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• 1992

Concept of primary solidification mode control was adopted to obtain optimal solidification crack resistance, hot ductility, corrosion resistance and toughness for austenitic stainless steel. By controlling primary solidification phase as primary $\delta$ and containing no ferrite at room temperature, optimal solidification crack resistance, hot ductility, corrosion resistance and cryogenic toughness could be obtained. The optimum chemical composition of austenitic stainless steel ranges 1.46~1.55(Creq/Nieq ratio) calculated by Schaeffler's equation.

• Corrosion Science and Technology
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• v.18 no.6
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• pp.258-266
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• 2019

The objective of this study was to evaluate corrosion resistance of additive manufactured 316L stainless steel and alloy 625 powders widely used in corrosion resistance alloys of marine industry in comparison with cast alloys. Directed Energy Deposition (DED) method was used in this work for sample production. DED parameter adjustment was also studied for optimum manufacturing and for minimizing the influence of defects on corrosion property. Additive manufactured alloys showed lower corrosion resistance in seawater compared to cast alloys. The reason for the degradation of anti-corrosion property was speculated to be due to loss of microstructural integrity intrinsic to the additive manufacturing process. Application of heat treatment with various conditions after DED was attempted. The effect of heat treatments was analyzed with a microstructure study. It was found that 316L and alloy 625 produced by the DED process could recover their expected corrosion resistance when heat treated at 1200 ℃.