환경인자 및 열처리조건에 따른 TiCode - 12 의 부식특성 연구

윤승열,김태영,이규환 한국부식방식학회 1991 Corrosion Science and Technology Vol.20 No.2

굴껍질에서 형성된 CaCO3 의 광물화 특성

윤승열,김용완,최청송 ( Seoung Yul Yun,Yong Wan Kim,Cheong Song Choi ) 한국화학공학회 1996 화학공학의이론과응용 Vol.2 No.2

환경인자 및 열처리조건에 따른 TiCode - 12 의 부식특성 연구

윤승열,김태영,이규환 한국부식학회 1989 Corrosion Science and Technology Vol.18 No.1

Corrosion behavior of TiCode-12 (Ti-0.8Ni-0.3Mo) has been studied by means of electrochemical polarization measurements and corrosion morphology examinations in various corrosive environments and different heat treatment conditions of the alloy. 1N H₂SO₄ at 45℃ was taken as a standard corrosive solution in which Cl^-, Fe^(3+) and Br^- ion were added to investigate their effects. Acid concentration and temperature were also varied. Polarization .behaviors of pure Ti, Ni, Mo and Ti₂Ni were compared with those of heat-treated TiCode-12 specimens to find out how the constituent elements and- the intermetallic compound formed during heat treatment of TiCode-12 affect the corrosion of the alloy. Mill-annealed TiCode-12 showed primary and secondary active-passive transition behavior in all the tested H₂SO₄ solutions. The former behavior was confirmed to be due to Ti and the latter due to Ni and Mo. The passive current densities increased with increased Cl^- ion concentration but decreased reversely beyond certain concentration. Fe^(3+) ion raised the corrosion potential of TiCode-12 to the passive region, thus reducing the corrosion rate. Br^- ion was turned out to be a critical species to induce the pitting of TiCode-12 by some unknown reason. Cathodic polarization behavior of pure Ni and Ti₂Ni revealed that hydrogen evolution reaction was promoted on these electrodes in acid media. This was ascribad to the cause for sensitization phenomena of TiCode-12 heat-treated in the temperature range in which the eutectoid reaction β→α + Ti₂Ni occurs. Near pits, observed on a sensitized TiCode-12 specimen immersed in H₂SO₄, always found were β crystals in which Ni peak was detected by EDS.

황동의 탈아연현상에 미치는 첨가원소의 영향

윤승열,이수완,송진태 한국부식학회 1981 Corrosion Science and Technology Vol.10 No.1

Dezincification phenomenon of 70% Cu-30% Zn brass containing small amounts of Sn (<1.7%) has been studied in 0.5M acidic chloride solutions. All the specimens used were prepared originally from electrolytic upper and zinc and chemical grade tin. Recording of potentiodynamic polarization curves and examination of the tnicrostracture for toe specimens in various conditions were main expeimetal techniques. Poteniodynamic polarization curves thus obtained revealed that 7/3 brags could initilly be dezincified either by selective dissolution of zinc or by copper redeposition mechanism depending on the electrode potential. Experimental results showed that addition of small amount of tin (from 0.74% up to 1.76%) to 7/3 brass could inhibit dezincification in case the copper reaeposition mechanism holds. This was found to be possible through that the added tin promotes hydrogen evolution reaction on the brass and this h.e.r. competes with copper redeposition retarding the latter. In other words. dezincification in 7/3 brass is replaced to general corrosion by the eddition of small amounts of tin. Microscopic examinations for the specimens which had been subjected to potentiostatic polarization at given potentials showed that the well-defined dezincfied layer could only be developed at elevated temperature (90℃), and in case the dezincified copper layer had already formed on the electrode surface. It was found through the microscopic examination of the dezincified dezincified specimen that the dezincification front occured in 7/3 brass was protruding along the grainboundaries in the brass matrix, indicating the latter was serving a a diffusion channel for the outgoing zinc aton to the electrode/solution interface.

승압하 인산연료전지 운전조건하에서 아세틸렌 블랙 탄소전극의 부식특성

윤승열,신진교 한국부식학회 1989 Corrosion Science and Technology Vol.18 No.1

Corrosion behavior of acetylene black binded with polytetrafluoroethylene at a weight ratio of 4 to 1 has been studied under phosphoric acid fuel cell conditions in a Teflon lined autoclave at elevated pressure using electrochemical polarization techniques. Corrosion currents were mainly measured potentiostatically at given potentials as a function of time. Experimental results showed that corrosion currents decreased as the pressure increased and at a given potential they increased with increasing temperature. Arrhenius plots of the corrosion currents measured at 0.9V vs. SCE displayed that the activation energy was 46.0 kJ/mole at H₃PO₄ concentrations of 100% and above whereas 36.4 kJ/mole at acid concentrations of 93% and below, indicating corrosion mechanism is changed with acid concentration. Corrosion current was also found to depend on water vapor pressure: it showed zero-order dependence above 97% H₃PO₄, then approximately first-order below 93%. There were also some experimental evidences on the existence of two anodic processes occurred in the corrosion of acetylene black.

연구논문초록(’81-’90) : 인산연료전지용 탄소재료의 전기화학적 분극특성

윤승열,신진교,정도양 한국부식학회 1991 Corrosion Science and Technology Vol.20 No.1

Electrochemical polarization behaviors, of various carbon electrodes were measured using potentiodynamic, potentiostatic and cyclicvoltametric method under phosphoric acid fuel cell conditions at ambient pressure. The carbon electrodes were made of various carbon sources such as carbon blacks bonded with polytetraffuoroethylene, commercial carbon papers, a glassy carbon and a graphite. The shape of potentiodynamic anodic polarization curves for the carbon electrodes could be classified into four types with different Tafal-like slopes and polarized current values depending on carbon species. The results of tests revealed that the larger the Tafel-like slope and current values, the greater the degree of disorder on the carbon surface. Measurements of current efficiency for CO₂ evolution and cyclic votamogram indicated that at least two anodic processes occurred in the corrosion of carbon : the evolution of CO₂ and the formation of a surface oxide. At all potentials a linear relationship was observed between logarithms of the potentiostatic anodic current, i and polarization time, t. The Slope of the log i vs. log t plot was dependent on carbon species and electrode potential. It had a larger value at lower potentials. This phenomenon was ascribed to the reduction of active sites on carbon surface as the polarization time elapsed.

도장강판의 내식성에 미치는 인산염 피막의 영향

윤승열,김진영,진영술,박찬섭 ( S . R . Yoon,Jin Young Kim,Yeong Sool Jin,Chan Sub Park ) 한국부식방식학회 1987 Corrosion Science and Technology Vol.16 No.1

황산 수용액 내에서 Pb - Ca 합금의 부식특성

윤승열,송인호,박영우 ( S . R . Yoon,I . H . Song,Y . W . Park ) 한국부식방식학회 1980 Corrosion Science and Technology Vol.9 No.2

산성 염소산카리 용액내에서 구리의 부식반응속도

윤승열 대한금속재료학회(대한금속학회) 1973 대한금속·재료학회지 Vol.11 No.1

염소산이온의 농도 0.001∼0.025molar, 온도범위 28°∼70℃에서 구리의 부식반응속도에 관하여 연구하였다. 산화반응속도는 용액내에 축적되는 구리이온의 양을 시간에 따라 측정하면서 조사하였고, 상온에서 구리시편의 전극전위 측정도 병행하였다. 용해반응이 일어나는 동안에 수소이온의 감소량은 생성된 구리이온 양의 두배로 나타났고 염소이온이 반응 생성물로 확인되었다. 용액내에 축적되는 구리이온의 양, [Cu^(++)]와 시간, t에 대한 log-log plot를 하면 다음과 같은 실험식을 얻을 수 있었다. [Cu^(++)]^(5/4)=s·(t-t_0) 여기에서 s와 t_0는 실험조건에 따르는 상수이며 특히 t_0는 구리시편의 표면처리에 따라 변하는 상수로 나타났다. 구리의 용해속도는 pH 0∼3.5 범위에서 수소이온 농도에 무관한 것으로 나타났다. 용해속도는 구리이온 농도와 용액의 pH가 Cu₂O를 형성하는 데 적합한 조건이 되었을 때 급격히 변화하는 것을 볼 수 있었다. 구리시편의 부식전위는 Cu/Cu^(++)평형전극전위의 값에 매우 가까운 값을 나타내었고, 초기 수조이온 농도가 일정할 때 염소산이온의 농도가 증가함에 따라 부식 전위가 증가하는 것이 관찰되었다. 구리의 용해속도는 염소산이온 농도에 1/2승에 의존하는 것을 알 수 있었다. 위에 관찰된 모든 현상에 알맞는 부식기구에 대한 가설은 염소산 이온이 구리시편에 흡착한 뒤 염소산이온 내부의 산소원자와 금속구리 사이에서 일어나는 charge transfer반응이 부식반응의 slow step이 되기 때문일 것이라고 생각하였다. 앞에 나타난 특이한 반응차수도 구리시편의 부식전위가 부식반응 속도에 영향을 주는 것으로 해석하여 이론적으로 유도할 수 있었다.

황산 수용액 내에서 Pb - Ca 합금의 부식특성

윤승열,박영우,송인호 한국부식학회 1981 Corrosion Science and Technology Vol.10 No.1

Corrosion behavior of Pb-Ca alloy in 7.9N aqueous sulfuric acic solution has been studied using potentiodynamic polarizaiion technique. Pb-0.76% Ca mother alloy and eutectic Pb-0.08% Ca were prepared originally from chemical grade Pb-powder and metallic Ca in the specially designed melting apparatus. The casted mother alloy, in which uniformly distributed Pb₃Ca dendrites had been impeded, showed remarkable increase in hardness compared with pure Pb ingot. The casted eutectic alloy aiso displayed much increase in hardness and the morphology of the two eutectic phases (primary alpha and Pb₃Ca) seemed to occur in lamellar form. Cyclic linear sweep voltammogram for the above Pb-Ca alloys indicated that such Ca addition into Pb did not change much the shape of polarization curve for pure Pb. However, when the charging-discharging simulation of lead-acid battery positive by continuous cyclic linear potential sweep technique was performed on the above Pb-Ca electrode between the limited potential range 1600-1200mV vs SCE, the polarization behavior became complicated, and distinguishable with the number of cycles and the amount of Ca addition. The reason of this has been explained theoretically considering various Pb-compound electrode reactions and their equilibrium potentials. Cyclic corrosion product morphology was also examined and has been discussed briefly.