• Journal of Surface Science and Engineering
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• v.42 no.2
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• pp.79-85
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• 2009

We aimed to develop a Fe-($16{\sim}19$)Cr-($0.1{\sim}0.6$)Ti-($0.1{\sim}0.6$)Nb stainless steel for automotive exhaust parts with high corrosion resistance. The alloys with high Cr content showed high resistance to general corrosion and also localized corrosion. The increase of Ti and Nb contents resulted in a linear increase in the general corrosion resistance, while the pitting potential was improved by addition of these elements up to about 0.4 wt.%. The low-carbon Fe-17Cr-0.4Ti-0.4Nb alloy annealed at $850^{\circ}C$ and air-cooled was considered to be the optimum alloy for our purpose with the critical anodic current density of $247{\mu}A/cm^2$ in 0.05 M $H_2SO_4$ solution and the pitting potential of 310 mVSCE in 0.2 M NaCl solution.

• Journal of Surface Science and Engineering
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• v.31 no.2
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• pp.73-80
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• 1998

The aim of this study is to develop sintered stainless steels (SSS) with good mechanical strength, wear resistance, and corrosion resistance by nitrogen ion implantation on the Culated SSS surface. Stainless steel compacts containg Cu (2-10 wt%) were prepared by electroless Cu-pating method which results in the increased3 homogenization in alloying powder. Nitrogen ion implantation was carried out by using N2 gas as the ion source. Nitrogen ions were embedded by an acceleratol of 130keV with doese $3.0\times10^{17}\;ions/\textrm{cm}^2$ on the SSS at $25^{\circ}C$ in$2\times10^{-6}$ torr vacuum. The nitrogen ion implanted SSS obtained from anodic ploarization curves revealed higher corrosion potential than that of nitrogen ion unimplante one. And nitrogen ion implanted 316LSSS had good resistance to pitting corrosion due to the synergistic effect of Mo and N, and the inhibition of $NH_4\;^+$<\TEX>, against $CI^-$<\TEX>.

• Journal of Korea Foundry Society
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• v.43 no.5
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• pp.230-240
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• 2023

The pitting corrosion behavior of 329LD cast lean duplex stainless steel and CF3M cast austenitic stainless steel was investigated in chloride environments. The pitting corrosion resistance of the 329LD alloy was superior to that of the CF3M alloy because the pitting potential, passive region, and critical pitting temperature of the low Ni-low Mo 329LD alloy were higher than those of the high Ni-medium Mo commercial CF3M alloy. There are two main reasons for the enhancement of the pitting corrosion resistance of high Cr-low Momedium N 329LD alloy compared to the low Cr-medium Mo CF3M alloy: First, the pitting resistance equivalent number (PREN_δ+γ) value of the 329LD alloy is higher than that of the CF3M alloy. Second, the passive region of the 329LD alloy is larger than that of the CF3M alloy. It indicates that the synergistic effect of the three elements by adding high Cr and low Mo-medium N to the 329LD alloy enhances the passivity of the passive film, thereby increasing the pitting corrosion resistance. It was verified that based on the PREN_γ of austenite (γ) and PREN_δ of ferrite (δ) values calculated using an N-factor of 16, the pitting corrosion of the 329LD alloy was selectively initiated at the γ-phases because PREN_γ value of austenite (γ) was smaller than that of ferrite (δ), and finally propagated from the γ-phase to the δ-phase.

• Journal of Surface Science and Engineering
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• v.53 no.5
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• pp.207-212
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• 2020

Silver is an inexpensive precious metal and is used in various jewelry in Asia. Although silver has high potential, it has corrosion resistance that is vulnerable to boiling sulfuric acid and nitric acid. So, silver research is needed to prevent the corrosion with environment. But silver corrosion is not studied. sulfuric acid make the uniform corrosion and chloride ion make the pitting corrosion. ICCP inhibits the corrosion because it offset electrons. This study used a potential from - 4 V to 4 V to check the effect of potential. Corrosion rate is lowet at -1 V.

• Journal of Surface Science and Engineering
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• v.37 no.5
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• pp.249-252
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• 2004

Effects of HA and TiN coating on the electrochemical characteristics of Ti-6AI-4V alloys for bone plates were investigated using various test methods. Ti-6AI-4V alloys were fabricated by using a vacuum induction furnace and bone plates were made by laser cutting and polishing. HA was made of extracted tooth sintered and then tooth ash was used as HA coating target. The TiN and HA film coating on the surface were carried on using electron-beam physical vapor deposition (EB-PVD) method. The corrosion behaviors of the samples were examined through potentiodynamic method in 0.9% NaCI solutions at $36.5\pm$$1^{\circ}C$ and corrosion surface was observed using SEM and XPS. The surface roughness of TiN coated bone plates was lower than that of tooth ash coated plates. The structure of TiN coated layer showed the columnar structure and tooth ash coated layer showed equiaxed and anisotrophic structure. The corrosion potential of the TiN coated specimen is comparatively high. The active current density of TiN and tooth ash coated alloy showed the range of about $1.0xl0^{-5}$ $A\textrm{cm}^2$, whereas that of the non-coated alloy was$ 1.0xl0^{-4}$ $A\textrm{cm}^2$. The active current densities of HA and TiN coated bone plates were smaller than that of non-coated bone plates in 0.9% NaCl solution. The pitting potential of TiN and HA coated alloy is more drastically increased than that of the non-coated alloy. The pit number and pit size of TiN and HA coated alloy decreased in compared with those of non-coated alloy. For the coated samples, corrosion resistance increased in the order of TiN coated, tooth ash coated, and non-coated alloy.

• Journal of Power System Engineering
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• v.19 no.6
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• pp.75-81
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• 2015

A deposited metal specimen of ER2594 which is a super duplex steel welding wire used to investigate the effect of sigma(${\sigma}$) phase on electrochemical corrosion characteristics was prepared by gas tungsten arc welding. Aging treatment was conducted for the specimen at the temperature range of $700^{\circ}C$ to $900^{\circ}C$ for 5 to 300 minutes after annealing at $1050^{\circ}C$. Corrosion current density has decreased a little with an increase of aging time over 60 minutes at $700^{\circ}C$ to $900^{\circ}C$ and the uniform corrosion of deposited metal had more influence on the precipitation of ferrite than the precipitation of sigma phase. Therefore, the precipitation of sigma phase did not have much effect on the uniform corrosion. Pitting potential representing pitting corrosion has shown decreasing tendency as the precipitation of sigma phase increased. The degree of sensitization representing intergranular corrosion has shown increasing tendency as the precipitation of sigma phase increased at $700^{\circ}C$ to $800^{\circ}C$, while it has decreased at $900^{\circ}C$ for 60 to 300 minutes.

• Corrosion Science and Technology
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• v.13 no.3
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• pp.87-94
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• 2014

Recently, the application of bending products has been increased since the industries such as automobile, aerospace, ships, and plants greatly need the usage of pipes. For facility fabrication, bending process is one of key technologies for pipings. Induction heat bending process is composed of bending deformation by repeated local heat and cooling. Because of local heating and compressive strain, detrimental phases may be precipitated and microstructural change can be induced. This work focused on the effect of induction heat bending process on the properties of ASME SA312 TP316 stainless steel. Evaluation was done on the base metal and the bended areas before and after heat treatment. Microstructure analysis, intergranular corrosion test including Huey test, double loop electropotentiokinetic reactivation test, oxalic acid etch test, and anodic polarization test were performed. On the base of microstructural analysis, grain boundaries in bended extrados area were zagged by bending process, but there were no precipitates in grain and grain boundary and the intergranular corrosion rate was similar to that of base metal. However, pitting potentials of bended area were lower than that of the base metal and zagged boundaries was one of the pitting initiation sites. By re-annealing treatment, grain boundary was recovered and pitting potential was similar to that of the base metal.

• Corrosion Science and Technology
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• v.19 no.5
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• pp.250-258
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• 2020

Recently, 5000 series and 6000 series Al alloys have been used as hull materials for small and medium-sized ships because of their excellent weldability, corrosion resistance, and durability in marine environments. Al ships can navigate at high speed due to their light weight. However, cavitation-erosion problems cause reducing durability of Al ship at high speed. In this investigation, 5052-O, 5083-H321, and 6061-T6 Al alloy materials were used to evaluate the damage characteristics with amplitude (cavitation strength). As a result of the electrochemical experiments, the corrosion current density and corrosion potential of 6061-T6 in seawater were 8.52 × 10-7 A/㎠ and -0.771 V, respectively, presenting the best corrosion resistance. The cavitation-erosion experiment showed that 5052-O had the lowest hardness value and cavitation-erosion resistance. 5052-O also had a very short incubation period. As the experiment progressed for 5052-O, pitting formed and grew in a short time, and was observed as severe cavitation-erosion damage that eliminated in large quantities. Among the three specimens, 5083-H321 presented the highest hardness value and the damage rate was the smallest after the initiation of pitting.

• Journal of Surface Science and Engineering
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• v.33 no.2
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• pp.93-100
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• 2000

Effects of Ti content and Ti underlayer on the pitting behavior of TiN coated AISI 304 stainless steel have been studied. The stainless steel containing 0.1~1.0wt% Ti were melted with a vacuum melting furnace and heat treated at $1050^{\circ}C$ for 1hr for solutionization. The specimen were coated with l$\mu\textrm{m}$ and 2$\mu\textrm{m}$ thickness of Ti and TiN by E-beam PVD method. The microstructure and phase analysis were conducted by using XRD, XPS and SEM with these specimen. XRD patterns shows that in TiN single-layer only the TiN (111) Peak is major and the other peaks are very weak, but in Ti/TiN double-layer TiN (220) and TiN (200) peaks are developed. It is observed that the surface of coating is covered with titanium oxide (TiO$_2$) and titanium oxynitride ($TiO_2$N) as well as TiN. Corrosion potential on the anodic polarization curve measured in HCl solution increase in proportion to the Ti content of substrate and by a presence of the Ti underlayer, whereas corrosion and passivation current densities are not affected by either of them. The number and size of pits decrease with increasing Ti content and a presence of the coated Ti film as underlayer in the TiN coated stainless steel.

• Journal of Welding and Joining
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• v.16 no.6
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• pp.59-68
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• 1998

In this study, effects of solidification modes (primary $\delta$-ferrite, primary ${\gamma}$-austenite) on the pit initiation and propagation in the 304L and 316L austenitic stainless steel weld metals were investigated. The solidification mode of weld metal was controlled by the addition of nitrogen to Ar shielding gas. Through the electrochemical experiments (potentiodynamic anodic polarization and potentiostatic time-current transient test) and metallographic examination (microstructure and elemental distribution), the following results were obtained. The more the volume content of nitrogen in the shielding gas were, the lower critical current density for passivity was observed. In comparison with weldments solidified through the primary $\delta$-ferrite solidification mode and the primary ${\gamma}$-solidification mode, the former showed higher critical pitting potential and a longer incubation time for stable pit initiation than the latter. However, in the pit propagation stage the former exhibited a faster dissolution rate than the latter. These results were believed to ee related to the distribution of alloying elements such as Cr, Mo, Ni and S.