수중 경화형도료의 부식특성에 관한 전기화학적 고찰

오민석(Min-Seok Oh),이명훈(Myung-Hoon Lee),이성렬(Syung-YUl Lee),김윤해(YUn Hae Kim),문경만(Kyung-Man Moon) 대한조선학회 2011 대한조선학회 학술대회자료집 Vol.2011 No.6

Many protection methods such as surface coating, electric protection or some other methods etc. have been applied to numerous steel structures being widely used in continental and marine areas to control corrosion of those structures in economic point of view. And most of those steel structures are mainly protected by coating methods. However, some steel piles being under seawater are generally protected by electric protection method, that is, either as an impressed current or as a sacrificial anode method. Furthermore, environmental contamination may be resulted in increasing severe corrosive environment, which, in turn, cause to be accelerated corrosion of the steel structures. Subsequrntly, coated steel structures would deteriorate more rapidly than the designed life time due to acid rain caused by air pollution etc. Therefore coating for the marine plant exposed to the seawater, that is, underwater hardening paintg is increasingly required to a fast dryness as well as a high corrosion resistance. In this study five types of underwater hardening paints are prepared with different resin series and additives. And their corrosion and water resistances were investigated with electrochemical methods such as corrosion potential, polarization curves, impedance and cyclic voltammogram measurements etc.. Even though, it is generally accepted that corrosion resistance of a bare steel tends to increase with shifting the corrosion potential in the noble direction, however, the corrosion resistance of the sample with coating relatively exhibited a better tendency when had lower corrosion potential in this study. Corrosion current density was also decreased with decreasing the diffusion limiting current density, which may mean that there is a somewhat relation between corrosion and water resistance. S sample of a ceramic resin series relatively showed the best corrosion as well as water resistance among those of samples, while the worst corrosion and water resistance were observed for the R sample of epoxy resin series. Corrosion and water resistance of those samples tended to be deteriorated with increasing immersion days, and their corrosion and water resistances are considered to be apparently improved by the types of resin and additives.

Cu-7Al-2.5Si 합금의 기계적 및 내식특성에 미치는 열처리 효과

오민석(Min-Seok Oh),이명훈(Myung-Hoon Lee),이성렬(Syung-YUl Lee),김윤해(YUn Hae Kim),문경만(Kyung-Man Moon) 대한조선학회 2011 대한조선학회 학술대회자료집 Vol.2011 No.6

Recently, the fuel oil of diesel engines of marine ships is being changed to heavy oil of low quality as the oil price is becoming higher and higher. Therefore, it is very important to purify the heavy oil which have a large amounts of impurities such as sediments, oxide compound and water etc. in order to operate smoothly a diesel engine with perfectly purified oil. Moreover, the spiral gear attached at the motor of the purifier which plays an important role to purify the heavy oil is also exposed to severe operation condition due to the purification of the heavy oil. Thus, the material of the spiral gear needs to a higher mechanical strength, wear and corrosion resistance. In this study, the heat treatment with constant holding time at temperature of 500℃ was carried out to the metarial of Cu-7Al-2.5Si series as centrifugal casted, and those properties for its material were inverstigated with observation of the microstructure and with electrochemical methods, such as measurement of corrosion potential, cathodic and anodic polarization curves, cyclic voltammogram, and impedance etc. in natural seawater solution. The α, β′ and γ2 phases were observed at the microstructure of its material as centrifugal casted in spite of no heat treatment due to quenching effect of a spin mold. However, their phases, that is, β′ and γ2phases were decreased gradually with heat treatment, in particular, the degree of decrement of their phases tended to increase with increasing the holding time at a constant temperature. The corrosion resistance was also improved with the heat treatment compared to no heat treatment, furthermore, the holding time is longer and longer, its corrosion resistance exhibited a better tendency. In addition, when the holding time was 48hrs, its corrosion current density showed the lowest value. The pattern of similar to a pitting corrosion was observed greatly at the its material surface in the case of no heat treatment, which is considered that γ2 phase of the grain boundary was corroded preferentially as an anode. However, the pattern of general corrosion exhibited increasingly due to decreasing the γ2 phase with heat treatment. Consequently, it is suggested that the metarial of Cu-7Al-2.5Si series can be improved with the heat treatment for the mechanical property and corrosion resistance.

수중 경화형도료의 부식특성에 관한 전기화학적 고찰

문경만(Kyung-Man Moon),오민석(Min-Seok Oh),이명훈(Myung-Hoon Lee),이성렬(Syung-Yul Lee),김윤해(Yun-Hae Kim) 한국해양공학회 2011 韓國海洋工學會誌 Vol.25 No.2

Many protection methods such as surface coating, electric protection, or other methods have been applied to the numerous steel structures widely used in continental and marine areas to control their corrosion, which is done from an economic point of view. Most of these steel structures are primarily protected by coating methods. However, some steel piles under seawater are protected by the electric protection method, that is, either using an impressed current or a sacrificial anode method. Furthermore, environmental contamination may cause a severely corrosive environment, which, in turn, causes the accelerated corrosion of steel structures. Subsequently, coated steel structures could deteriorate more rapidly than the designed lifetime because of the acid rain caused by air pollution, etc. Therefore, a coating of marine paint exposed to seawater, that is, underwater hardening painting, is increasingly required to be fast drying as well as highly corrosion resistant. In this study, five types of underwater hardening paints were prepared with different resin series and additives. Their corrosion and water resistances were investigated using electrochemical methods such as corrosion potential, polarization curves, impedance and cyclic voltammogram measurements, etc. Even though it is generally accepted that the corrosion resistance of bare steel tends to increase with a shift of the corrosion potential in the noble direction, the corrosion resistance of a sample with a coating exhibited a relatively better tendency when it had a lower corrosion potential in this study. The corrosion current density was also decreased with a decrease in the diffusion limiting current density, which may mean that there is some relationship between corrosion and water resistance. The S sample of the ceramic resin series showed the relatively best corrosion and water resistance among those of samples, while the worst corrosion and water resistance were observed for the R sample of the epoxy resin series. The corrosion and water resistance of those samples tended to deteriorate with an increase in the immersion days, and their corrosion and water resistances were considered to be apparently improved by the types of resin and additives.

22 APU 스텐레스강의 용접부위의 부식특성에 관한 전기화학적 평가

김진경(Jin-Gyeong Kim),문경만(Kyung-Man Moon),김윤해(Yun-Hae Kim),이성렬(Syung-Yul Lee),김종도(Jong-Do Kim),이명훈(Myung-Hoon Lee) 한국마린엔지니어링학회 2009 한국마린엔지니어링학회 학술대회 논문집 Vol.2009 No.-

Two kinds of welding methods was carried out to 22 APU stainless steel, one is a Laser welding and the other is the TIC welding. Vickers hardness of all welded zone(WM:Weld Metal, HAZ:Heat Affected Zone, BM:Base Metal)in case of Laser welding showed a relatively higher value than those of TIC welding. Futhermore their corrosion current density in all welding zone were also observed with lower values compared to TIC welding. In particular corrosion currenl density of WM with TIC welding indicated the highest value than those of other welding zone, Consequently we can see that corrosion resistance of all welding zone of 22 APU stainless steel can apparently be improved by using of Laser welding.