• Journal of Magnetics
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• v.16 no.3
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• pp.304-307
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• 2011

High performance Nd-Fe-B magnets can be manufactured by both sintering and hot deformation. The corrosion behaviors of the magnets prepared by the two processes were compared. Effect of microstructure on the corrosion resistance of Nd-Fe-B magnets was also investigated. A neutral salt spray test (NSS) was performed for the different-processed magnets. The weight losses of the samples after the corrosion test were measured. The corrosion microstructures were observed using a scanning electron microscope. It shows that the corrosion resistance of hot deformed magnets is much better than that of the sintered ones because the grain size and the distribution of Nd-rich phases of the hot deformed magnets are much finer and more uniform than those of the sintered ones. The different microstructure between the sintered and the hot deformed magnets causes the different corrosion behavior.

• Corrosion Science and Technology
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• v.2 no.6
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• pp.253-259
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• 2003

Zirconium based alloys have been extensively used as a cladding material for fuel rods in nuclear reactors, due to their low thermal neutron absorption cross-section, excellent corrosion resistance and good mechanical properties at high temperatures. However, a cladding material for fuel rods in nuclear reactors was contact water during long time at high-temperature, so it is necessary to improve the wear and corrosion resistance of the fuel cladding, At ambient environment, there are few data or paper on the characteristic of corrosion in chloride solution and acidic solution. The specimens used in this work are pure Zr and Zircaloy-4. Zircaloy-4 is a specific zirconium-based alloy containing, on a weight percent basis, 1.4% Sn, 0.2% Fe, 0.1% Cr. Pitting corrosion resistance of two alloys by ASTM G48 is higher than that of electrochemical method. Passive film formed on Zircaloy-4 is mainly composed of $ZrO_2$, metallic Sn, and iron species regardless of formation environments. Also, passive film formed on Zr alloys shows n-type semiconductic property on the base of Mott-Schottky plot.

• Journal of the Korean institute of surface engineering
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• v.51 no.6
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• pp.354-359
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• 2018

NaCl-induced hot corrosion behavior of ASTM T22 (Fe-2.25Cr-1Mo), T91 (Fe-9Cr-1Mo), T92 (Fe-9Cr-1.8W-0.5Mo), 347HFG (Fe-18-Cr-11Ni), and 310H (Fe-25Cr-19Ni) steels was studied after spraying NaCl on the surface. During corrosion at $600-800^{\circ}C$ for 50-100 h, thick, non-adherent, fragile, somewhat porous oxide scales formed. All the alloys corroded fast with large weight gains owing to fast scaling and destruction of protective oxide scales. Corrosion rates increased progressively as the corrosion temperature and time increased. Corrosion resistance increased in the order of T22, T91, T92, 347HFG, and 310H, suggesting that the alloying elements of Cr, Ni, and W beneficially improved the corrosion resistance of steels. Basically, Fe oxidized to $Fe_2O_3$, and Cr oxidized to $Cr_2O_3$, some of which further reacted with FeO to form $FeCr_2O_4$ or with NiO to form $NiCr_2O_4$.

• Corrosion Science and Technology
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• v.19 no.6
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• pp.318-325
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• 2020

Generally, Al alloys of 5000 and 6000 series show excellent weldability, workability, and specific strength, and are widely used in ship building. A combined experiment via cavitation erosion and corrosion damage involving 6061-T6 Al alloy was performed using potentiodynamic polarization under cavitation erosion (hybrid experiments) with amplitude (cavitation strength). The corrosion current density was approximately 52-fold higher at 30 μm than under static conditions, suggesting that the amplitude greatly affected the damage. The degree of damage increased with increasing cavitation amplitude. After the hybrid experiment, the corrosion rate was compared according to the weight loss and damage depth, and the relationship between the two values was expressed as alpha value. The alpha (α) values at amplitudes of 5 μm, 10 μm and 30 μm were 5.11, 12.81 and 8.74, respectively, suggesting that the α value at 10 μm was greater than at 5 μm, and indicating local corrosion damage. However, the α value at 30 μm was smaller than that of 10 μm, which is attributed to higher damage via uniform corrosion than damage induced by local corrosion.

• Korean Journal of Materials Research
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• v.32 no.5
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• pp.280-286
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• 2022

Corrosion is a natural, inevitable process, and is one of the world's most serious problems. Losses incurred due to corrosion are extremely expensive for society. Several technological strategies have been explored and implemented to address these losses. The use of inhibitors to prevent corrosion is a common and efficient method to reduce corrosion losses. This review covers Al and Al-composite corrosion inhibitors in chloride-containing solutions, because of their popularity in a broad array of industrial applications. A vast number of studies in the literature detail the common tendency of Al and Al-composites with reinforcements to deteriorate. Accordingly, it is worthwhile to employ inhibitors to protect them, as discussed in the present work. The emphasis is on selecting the smartest corrosion inhibitor and evaluating its performance. According to the study, the most commonly used corrosion inhibitors are 1,4-naphthoquinone (NQ), 1,5-naphthalene diol, 3-amino-1,2,4-triazole-5-thiol (ATAT), ammonium tetrathiotungstate, clotrimazole, amoxicillin, antimicrobial and antifungal drugs. Electrochemical impedance spectroscopy (EIS), potentiodynamic (PDP), and weight loss were among the most commonly used modern electrochemical technologies to test inhibitors' efficacy under environmental conditions.

• Corrosion Science and Technology
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• v.22 no.3
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• pp.175-186
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• 2023

Effects of high-temperature environment and low-temperature environment on corrosion behaviours of 18Cr stainless steels (type 304L, type 441) in simulated selective catalytic reduction (SCR) environments were studied using weight loss test in each environment and rust analysis. With time to exposure to the high-temperature environment, type 441 was more resistant to corrosion than type 304L due to both higher diffusivity of Cr and lower thermal expansion coefficient in α-iron. The former provides a stable protective Cr₂O₃ layer. The latter leaded to low residual stress between scale and steel, reducing the spallation of the scale. With time to exposure to the low-temperature environment, on the other hand, type 304L was more resistant to corrosion than type 441. The lower resistance of type 441 was caused by Cr-depleted zone with less than 11% formed during the pre-exposure to a high-temperature environment, unlike type 304L. It was confirmed by results from the crevice corrosion test of sensitised 11Cr steel. Hence, to achieve higher corrosion resistance in simulated SCR environments, ferritic stainless steels having lower thermal expansion coefficient and higher diffusivity of Cr but containing more than 18% Cr are recommended.

• Journal of the Korean institute of surface engineering
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• v.41 no.3
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• pp.121-128
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• 2008

High strength 7xxx aluminum alloys have been applied to automotive bump back beam of the some limited model for light weight vehicle. The aluminum bump back beam is manufactured through extrusion, bending and welding. The residual stress given on these processes combines with the corrosive atmosphere on the road spreaded with corrosive chemicals to melt snow to occur the stress corrosion cracking. The composition of commercial 7xxx aluminum has Zn/Mg ratio about 3 and Cu over 2 wt% for better strength and stress corrosion cracking resistivity. But this composition isn't adequate for appling to the automotive bump back beam with high resistance to extrusion and bad weldability. In this study the composition of 7xxx aluminum alloy was modified to high Zn/Mg ratio and low Cu content for better extrusion and weldability. To estimate the resistivity against stress corrosion cracking of this aluminum alloy by slow strain rate test, the corrosion atmosphere and strain rate separate the stress corrosion cracking from conventional corrosion must be investigated. Using 0.6 Mol NaCl solution on slow strain rate test the stress corrosion cracking induced fracture was not observed. By adding 0.3% $H_2O_2$ and 0.6M $Na_2SO_4$ to 1M NaCl solution, the corrosion potential and current density of polarization curve moved to active potential and larger current density, and on the slow strain rate test the fracture energy in solution was lower than that in pre-exposure. These mean the stress corrosion cracking induced fracture can be estimated in this 1M NaCl + 0.3% $H_2O_2$ + 0.6M $Na_2SO_4$ solution. When the strain rate was below $2{\times}10^{-6}$, the stress corrosion cracking induced fracture start to be observed.

• Corrosion Science and Technology
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• v.8 no.1
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• pp.1-10
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• 2009

The influence of Schiff bases on the corrosion inhibition of mild steel in 1 M $H_2SO_4$ have been investigated by weight loss, gasometry, impedance and polarization techniques. The results obtained reveal that these compounds act as good inhibitors. The inhibition efficiency of Schiff bases increased with concentration and synergistically increased on addition of chromate, sulphate and halide ions. Potentiodynamic polarization measurements clearly reveal that the investigated inhibitors are of mixed type but they are more cathodic in nature. The adsorption of these compounds on mild steel surface for both the acids were found to obey Langmuir adsorption isotherm. The surface morphology was studied by SEM and UV reflectance spectra.

• Journal of Electrochemical Science and Technology
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• v.4 no.2
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• pp.47-56
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• 2013

Inhibition performance of Lornoxicam & Tenoxicam against corrosion of carbon steel in 1M $H_2SO_4$ solutions was investigated by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements. The inhibition efficiency increased with increasing inhibitor's concentration, but decreased with increase in temperature. Potentiodynamic polarization curves showed that, the inhibitors were of mixed type. The apparent activation energy ($E^*_a$) and other thermodynamic parameters for the corrosion process have also been calculated and discussed. The inhibition of carbon steel corrosion is due to the adsorption of the inhibitor molecules on the surface, which follows Temkin adsorption isotherm. The mechanism of inhibition was discussed in the light of the chemical structure of the undertaken inhibitors.

• Journal of Fisheries and Marine Sciences Education
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• v.15 no.1
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• pp.115-122
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• 2003

Generally, material for radiator of automobile is composed of Al-alloy, but part of radiator material is still composed of Cu. Specially, Al-alloy replaces Cu and Cu-alloy as cooling and heating system material for light weight. Therefore, galvanic electronic cell is formed between Al-alloy and Cu for automobile radiator material, and Al-alloy corrosion is accelerated. So, in this study, galvanic corrosion test of Al-alloy coupling with Cu was carried out in distilled water, tap water, polluted environment and non-freezing solution. And thus corrosion potential and galvanic currrent density of Al-alloy coupling with Cu is investigated.