• Nuclear Engineering and Technology
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• v.40 no.6
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• pp.505-510
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• 2008

The correlation between the tensile strength and corrosion behavior of Zr-1.0wt%Nb alloy heat treated at $480^{\circ}C$ for up to 32 hours was evaluated. The tensile strength at $400^{\circ}C$ was continuously reduced with an increasing heat treatment time, mainly due to a grain growth and a decreased area fraction of the precipitates. However, the corrosion resistance in an aqueous ammonia solution at $360^{\circ}C$ was enhanced, mainly due to the formation of $\beta$-Nb precipitates. It is thus concluded that a longer heat treatment time provides a better corrosion resistance while degrading the tensile strength.

• Korean Journal of Materials Research
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• v.14 no.11
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• pp.813-820
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• 2004

The electrolytic reduction of spent oxide fuel involves the liberation of oxygen in a molten LiCl electrolyte, which is a chemically aggressive environment that is very corrosive for typical structural materials. So, it is essential to choose the optimum material for the process equipment handling molten salt. In this study, corrosion behavior of Haynes 263, 75, and Inconel X-750, 718 in molten salt of $LiCl-Li_{2}O$ under oxidation atmosphere was investigated at $650^{\circ}C\;for\;72\sim360$ hours. At $3\;wt\%\;of\;Li_{2}O$, Haynes 263 alloy showed the highest corrosion resistance among the examined alloys, and up to $8\;wt\%\;of\;Li_{2}O$, Haynes 75 exhibited the highest corrosion resistance. Corrosion products were formed $Li(Ni,Co)O_2,\;LiNiO_2\;and\;LiTiO_2\;and\;Cr_{2}O_3$ on Haynes 263, $Cr_{2}O_3,\;NiFe_{2}O_4,\;LiNiO_2,\;Li_{2}NiFe_{2}O_4,\;Li_{2}Ni_{8}O_10$ and Ni on Haynes 75, $Cr_{2}O_3,\;(Al,Nb,Ti)O_2,\;NiFe_{2}O_4,\;and\;Li_{2}NiFe_{2}O_4$ on Inconel X-750 and $Cr_{2}O_3,\;NiFe_{2}O_4\;and\;CrNbO_4$ on Inconel 718, respectively. Haynes 263 showed local corrosion behavior and Haynes 75, Inconel X-750, 718 showed uniform corrosion behavior.

• Corrosion Science and Technology
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• v.14 no.6
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• pp.288-295
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• 2015

The present work addresses crevice and galvanic corrosion processes occurring at the cylinder head gasket/cylinder head interface and cylinder head gasket/cylinder liner interface of four-stroke medium-speed diesel engines for marine applications. The contact between these systems and the marine environment can promote formation of demanding corrosion conditions, therefore influencing the lifetime of the engine components. The electrochemical behavior of various metals and alloys used as head gasket materials (both ferrous alloys and copper alloys) was investigated. The efficacy of corrosion inhibitors was determined by comparing electrochemical behavior with and without inhibitors. In particular, crevice corrosion has been investigated by electrochemical tests using an experimental set-up developed starting from the requirements of the ASTM G-192-08, with adaptation of the test to the conditions peculiar to this application. In addition to the crevice corrosion resistance, the possible problems of galvanic coupling, as well as corrosive reactivity, were evaluated using electrochemical tests, such as potentiodynamic measurements. It was possible to quantify, in several cases, the corrosion resistance of the various coupled materials, and in particular the resistance to crevice corrosion, providing a basis for the selection of materials for this specific application.

• Nuclear Engineering and Technology
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• v.52 no.6
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• pp.1222-1230
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• 2020

The corrosion rates of the reactor pressure vessel materials of SA508 Grade 3 were measured using a weight loss method in aerated boric acid solutions to simulate the evaporation of leaked PWR primary water in an ambient environment. The corrosion behavior and products were examined using X-ray diffraction and electron microscopy. SA508 showed typical general corrosion characteristics. The corrosion rate increased steadily as the boron concentration was increased. As the immersion time elapsed, the corrosion rate slowly or rapidly decreased according to the oxidation reaction of iron. The corrosion rate showed a complicated pattern depending on the temperature; it increased gradually and then rapidly decreased again when reaching a certain transition temperature. The corrosion products of SA508 were found to be FeO(OH), Fe₂O₃, and Fe₃O₄. As the boron concentration decreased and the temperature was increased, the formation of Fe₃O₄ was more favorable as compared to the formation of FeO(OH) and Fe₂O₃. Consequently, the changes of the corrosion rate and behavior were closely related to the oxidation reaction of iron on the surface. The corrosive damage to SA508 appears to be most severe when the oxidation reaction is such that Fe₂O₃ forms as a corrosion product.

• Journal of the Korean Institute of Gas
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• v.9 no.1 s.26
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• pp.21-25
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• 2005

This paper was studied on the corrosion behavior of STS 304 for gas boiler in the condensed water, the electrochemical polarization test of STS 304 for gas boiler in the condensed water was carried out. And the corrosion behavior of STS 304 was considered. The main results are as following: 1) As corrosion environment is acidified from neutrality, the polarization resistance of STS 304 decreases and the corrosion potential is less noble. 2) The corrosion reaction mechanism of STS 304 is cathodic control. 3) As corrosion environment is acidified, the passive potential range of STS 304 decreases. Also, the passive current density of STS 304 increases.

• Corrosion Science and Technology
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• v.13 no.2
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• pp.48-55
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• 2014

Influence of annealing temperature on the microstructure and resistance to pitting corrosion of the hyper duplex stainless steel was investigated in acid and neutral chloride environments. The pitting corrosion resistance is strongly dependent on the microstructure, especially the presence of chromium nitrides ($Cr_2N$), elemental partitioning behavior and volume fraction of ferrite phase and austenite phase. Precipitation of deleterious chromium nitrides reduces the resistance to pitting corrosion due to the formation of Cr-depleted zone. The difference of PREN (Pitting Resistance Equivalent Number) values between the ferrite and austenite phases was the smallest when solution heat-treated at $1060^{\circ}C$. Based on the results of electrochemical tests and critical crevice temperature tests, the optimal annealing temperature is determined as $1060^{\circ}C$.

• Journal of Advanced Marine Engineering and Technology
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• v.15 no.4
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• pp.22-28
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• 1991

The crevice corrosion behavior on austenitic AISI 304 and 316L stainless steel welded by TIG, MIG, $CO_2$ and SMA was studied. The results are as follows : In 10% $FeCl_3$ solution and natural sea water sampled near Mokpo port, the base metal of 304 stainless steel showed small amount corrosion, whereas 316L stainless steel did not showed any corrosion in the test periods. The weight loss caused by crevice corrosion increased with increasing weld heat input and residual .delta. ferrite formed in welded part. The corrosion resistance of the welded part was in the order of TIG, MIG, $CO_2$ and SMA. From this tendency, it is proved that the smaller heat input gives the better corrosion resistance.

• Corrosion Science and Technology
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• v.8 no.4
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• pp.139-142
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• 2009

Recently, quaternary titanium alloys of the system Ti-Nb-Ta-Zr received considerable research interest as potential implant materials because of their excellent mechanical properties and biocompatibility. However, only few reported works were available on the corrosion behavior of such alloys. Hence, in the present work, electrochemical corrosion of Ti-35Nb-5Ta-7Zr alloy, which has been fabricated by arc melting and heat treatment, was studied in 0.9 wt% NaCl at $37\pm1^{\circ}C$, along with biomedical grade Ti-6Al-4V and CP-Ti. The phase and microstructure of the alloys were investigated employing XRD and SEM. The results of electrochemical studies indicated that the corrosion resistance of the quaternary alloy was inferior to that of Ti-6Al-4V and CP Ti.

• Journal of Fisheries and Marine Sciences Education
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• v.17 no.1
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• pp.106-114
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• 2005

This paper is a study on the prevention of crevice corrosion for a stainless steel heat exchanger in various pH solutions and with Cl ion concentrations. The electrochemical polarization test and crevice corrosion test of STS 304 for a heat exchanger were carried out. The crevice corrosion aspect, a passive behavior, crevice corrosion behavior, and corrosion protection characteristics of STS 304 using Al-alloy and Mg-alloy galvanic anode were considered. The main results are as follows: 1. The crevice corrosion of STS 304 occurs in the crevice and this corrosion increases pitting according to depth direction. On the other hand, the exterior crevice becomes passive. 2. With changing from a neutral to acid environment and increasing Cl ion concentration, the pitting potential of STS 304 lowers, and thus the crevice corrosion of STS 304 is sensitive. 3. The cathodic protection potential of STS 304 in the crevice is cathodically polarized by increasing Cl ion concentration. Therefore, an Al-alloy galvanic anode is more suitable than a Mg-alloy galvanic anode to protect the crevice corrosion of STS 304.

• Nuclear Engineering and Technology
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• v.49 no.4
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• pp.769-775
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• 2017

The corrosion behavior of stainless steel (304 and 316 type) and copper induced by LiCl-KCl at low temperatures in the presence of sufficient oxygen and moisture was investigated through a series of experiments (at $30^{\circ}C$, $40^{\circ}C$, $60^{\circ}C$, and $80^{\circ}C$ for 24 hours, 48 hours, 72 hours, and 96 hours). The specimens not coated on one side with an aqueous solution saturated with LiCl-KCl experienced no corrosion at any temperature, not even when the test duration exceeded 96 hours. Stainless steel exposed to LiCl-KCl experienced almost no corrosion below $40^{\circ}C$, but pitting corrosion was observed at temperatures above $60^{\circ}C$. As the duration of the experiment was increased, the rate of corrosion accelerated in proportion to the temperature. The 316 type stainless steel exhibited better corrosion resistance than did the 304 type. In the case of copper, the rate of corrosion accelerated in proportion to the duration and temperature but, unlike the case of stainless steel, the corrosion was more general. As a result, the extent of copper corrosion was about three times that of stainless steel.