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산성 황산제이철 용액내에서 304 스테인레스강의 동전위 분극특성
윤승열 대한금속재료학회(대한금속학회) 1976 대한금속·재료학회지 Vol.14 No.3
25℃, 10 v/o 황산용액내에서 철3가 이온의 농도를 변화시키면서 304 스테인레스강의 동전위 분극곡선을 측정하였다. 용액은 교반하지 않고 대기와 접촉시켜 두었고 電位 走査속도는 600mV/min로 하였다. 분극곡선을 검토하여 본 결과 분극특성은 대체로 混成電位說에서 예측할 수 있는 바와 같이 변하였고 철3가 이온이 鋼표면에 흡착되어 강의 용해량이 감소된다고 해석할 수 있는 현상도 나타내었다. 또 철3가 이온의 환원속도는 넓은 전위범위에 걸쳐 확산에 의하여 지배되는 것을 알 수 있었다. 강의 분극과정에서 일단 형성된 부동태피막은 아주 안정하여서 재차 active 상태에 놓이어도 쉽사리 용해되지 않았고, 부동태 영역에서 부동태피막이 철3가이온에 의해서 용해되는 반응의 전기화학적 變數들도 검토하여 보았다. 철3가이온을 가하였을 때 active peak와 酸素發生전위는 실험오차내에서 변하지 않았다. Potentiodynamic polarization behavior of 304 stainless steel has been recorded with a scan rate of 600mV/min in 25℃, stagnant 10 v/o sulfuric acid solutions containing various concentrations of ferric ion. The shape of the polarization curves was changed in that manner generally predicted by the mixed potential theory, but analyses of them revealed that the adsorption of ferric ion on the electrode surface was occurring. Reduction of ferric ion proceeded at a diffusion limited rate over a wide range of electrode potential. The passive film once formed in the course of potential scan from active to noble side appeared so stable as to reduce the active peak current to a small value during the repeated potential scan. Some electrochemical parameters related to the dissolution of passive film by ferric ion was also examined. Active peak potential and oxygen evolution potential were little changed with the addition of ferric ion in the limit of experimental error.
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.
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.