• Journal of Technologic Dentistry
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• v.26 no.1
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• pp.35-40
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• 2004

In order to understand alloying effects on the corrosion resistance of Ti-(10$\sim$20)%Zr-(2$\sim$8%)Nb-0.2%Pd alloys, Polarization curves were measured at 5%HCI solution. The results were interpreted in terms of two parameters obtained by the molecular orbital calculation ; one is the bond order($B_{\circ}$) and the other is the metal d-orbital level($M_{d}$). $B_{\circ}$ is a measure of the strength of covalent bonds between titanium and alloying elements. $M_{d}$ is correlative with the electronegativity of elements. It was found that increasing of Zr and Nb with higher $B_{\circ}$ values showed a lower critical anodic current density in the polarization curve and hence higher corrosion resistance. On the other hand, increasing of Zr and Nb with higher $M_{d}$ values showed a higher corrosion resistance.

• Corrosion Science and Technology
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• v.10 no.2
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• pp.60-64
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• 2011

Lean duplex stainless steels have been developed in Korea for the purpose of being used in the seawater systems of industry. There are also many important seawater systems in nuclear power plants. These systems supply seawater to cooling water condenser tubes, heat exchanger tubes, related pipes and chlorine injection systems. The flow velocity of some part of seawater systems in nuclear power plants is high and damages of components from corrosion are severe. The considered lean duplex stainless steels are STS329LD (20.3Cr-2.2Ni-1.4Mo) and STS329J3L (22.4Cr-5.7Ni-3Mo) and PRENs of them are 29.4 and 37.3 respectively. Physical, mechanical and micro-structural properties of them are evaluated, and electrochemical corrosion resistance is measured quantitatively in NaCl solution. Critical Pitting Temperatures (CPT)s are measured on these alloys and pit depths are evaluated using laser microscope. Long period field tests on these alloys are now being performed, and some results are going to be presented in the following study.

• Corrosion Science and Technology
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• v.19 no.6
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• pp.302-309
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• 2020

This study aimed to predict the pitting corrosion characteristics of AL-6XN super-austenitic steel using multiple linear regression. The variables used in the model are degree of sensitization, temperature, and pH. Experiments were designed and cyclic polarization curve tests were conducted accordingly. The data obtained from the cyclic polarization curve tests were used as training data for the multiple linear regression model. The significance of each factor in the response (critical pitting potential, repassivation potential) was analyzed. The multiple linear regression model was validated using experimental conditions that were not included in the training data. As a result, the degree of sensitization showed a greater effect than the other variables. Multiple linear regression showed poor performance for prediction of repassivation potential. On the other hand, the model showed a considerable degree of predictive performance for critical pitting potential. The coefficient of determination (R2) was 0.7745. The possibility for pitting potential prediction was confirmed using multiple linear regression.

• Computers and Concrete
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• v.21 no.4
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• pp.419-429
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• 2018

Climate changes, such as increasing of $CO_2$ concentration and global warming, will impact on the carbonation service life of concrete structures. Moreover, slag blended concrete has a lower carbonation resistance than control concrete. This study presents a probabilistic numerical procedure for evaluating the impact of climate change on carbonation service life of slag blended concrete. This numerical procedure considers both corrosion initiation period and corrosion propagation period. First, in corrosion initiation period, by using an integrated hydration-carbonation model, the amount of carbonatable substances, porosity, and carbonation depth are calculated. The probability of corrosion initiation is determined through Monte Carlo method. Second, in corrosion propagation period, a probabilistic model is proposed to calculate the critical corrosion degree at surface cracking, the probability of surface cracking, and service life. Third, based on the service life in corrosion initiation period and corrosion propagation period, the whole service life is calculated. The analysis shows that for concrete structures with 50 years service life, after considering climate changes, the service life reduces about 7%.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.585-588
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• 2008

To predict the service life of reinforced concrete structures exposed to chloride environment, quantitative measures of material properties such as the critical chloride content for corrosion in concrete and the diffusion coefficient of chloride ions of concrete and the surface chloride content of the concrete are essential. However, it should be noted that they are influenced by several factors such as concrete mix proportions, cement type, and environmental conditions, etc. Thus, the purpose of this research is to estimate more actually the critical chloride content for corrosion of the reinforcing steel in concrete by field exposure experiment. For this purpose, the prism concrete test specimens were made for water-cement(W/C) ratios of 31%, 42%, 50%, and 70%, and then the field exposure experiment for them were conducted at Youngduk of the east coast for about 3 years. During the test, corrosion monitoring by half cell potential method was carried out to detect the time to initiation of corrosion for test specimens and its chloride content was evaluated by breaking the concrete test specimens when corrosion of the reinforcing steel in concrete was perceived. It was observed from the test results that the critical chloride content for corrosion of reinforcing steel in concrete would be dependent on W/C ratio and almost irrespective of concrete cover.

• 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 $1060^{\circ}C$.

• Corrosion Science and Technology
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• v.15 no.2
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• pp.54-57
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• 2016

Magnesium alloys have been extensively studied in recent years for potential biodegradable implant applications. A great deal of work has been done on the evaluation of the corrosion behaviour of magnesium alloys under in vitro and in vivo conditions. However, magnesium alloys, in general, contain secondary phase particles distributed in the matrix and/or along the grain boundaries. Owing to their difference in chemistry in comparison with magnesium matrix, these particles may exhibit different corrosion behaviour. It is essential to understand the corrosion behaviour of secondary phase particles in magnesium alloys in physiological conditions for implant applications. This paper critically reviews the biodegradation behaviour of secondary phase particles in magnesium alloys.

• Corrosion Science and Technology
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• v.3 no.5
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• pp.179-186
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• 2004

Recently the alloy development of duplex stainless steel has been done. On this study we studied the effect of the corrosion resistance according to the composition variety of C, Cr, N in the alloy elements of duplex stainless steel. materials which have below 0.1[mm/year] corrosion rate enable to use for corrosion-resisting materials, generally. On this experiment we inspected the effect of the composition variety of C, Cr, N in duplex stainless steel and the heat treatment, which the condition was the water quenching after the heat treatment for 1hr. The experiment was done on the basis of the ASTM G48A test, Critical pitting temperature(CPT), and ASTM G-61(Electrochemical tests for cyclic polarization).

• Structural Engineering and Mechanics
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• v.59 no.5
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• pp.795-802
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• 2016

Gas pipelines are types of structures that are highly susceptible to corrosion. Sometimes, the pipes are subjected to a thinning of the wall thickness at the inside or outside wall due to erosion/corrosion. Therefore, it is important to evaluate the strength of the pipes undergoing corrosion to maintain the integrity of the piping systems. The main purpose of this study is to understand failure aspects caused by degradation of metal due to corrosion through. The ASME standard offers a relationship for the yielding pressure of the corroded pipes which was compared with the finite element results. The results demonstrate to obtain accurate results, the ASME relationship is unreliable. Moreover, pitting corrosion must be considered critical more than of other types.

• Corrosion Science and Technology
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• v.18 no.3
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• pp.92-101
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• 2019

This study investigates how rivet head height affects the corrosion performance of carbon fiber reinforced plastic (CFRP) to aluminum alloy self-piercing riveted joints. Specimens with two different head heights were prepared. A rivet head protruding out of the top CFRP laminate forms the proud head height while a rivet head penetrating into the top CFRP generates the flush head height. The salt spray test evaluated corrosion performance. The flush head joints suffered from severe corrosion on the rivet head. Thus, the tensile shear load of flush head joints was substantially reduced. Electrochemical corrosion tests investigated the corrosion mechanisms. The deeper indentation of the flush head height damaged the CFRP around the rivet head. The exposure of damaged fibers from the matrix increased the cathodic potential of local CFRP. The increased potential of damaged CFRP accelerated the galvanic corrosion of the rivet head. After the rivet head coating material corroded, a strong galvanic couple was formed between the rivet head base metal (boron steel) and the damaged CFRP, further accelerating the flush rivet head corrosion. The results of this study suggest that rivet head flushness should be avoided to enhance the corrosion performance of CFRP to aluminum alloy self-piercing riveted joints.