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Nakayama S.,Sumitomo Electric Industries | Sugihara T.,Sumitomo Electric Industries | Notoya T.,Japan Copper and Brass Association | Osakai T.,Kobe University
Zairyo to Kankyo/ Corrosion Engineering | Year: 2013

A new voltammetric method for determination of the oxides on tin was proposed. In an ammonia buffer solution (0.5 M NH4OH)0.5 M NH 4Cl), well-defined reduction peaks for SnO and hydrated SnO 2 (denoted as SnO2-nH2O) were observed in a current-potential curve. The peak potentials were fully separated by -0.3 V, since NH4 + ions facilitated the reduction of SnO 2-nH2O. On the other hand, in a borate buffer solution, which has been frequently used as the supporting electrolyte for this purpose, and in 1 M KCl containing higher concentration of ions, the peak of SnO 2-nH2O was not detected. By using the ammonia buffer solution, we found that the main corrosion products formed on tin in air were SnO and SnO2-nH2O. It was also found that SnO was formed in air at a temperature higher than 100, while SnO2-nH2O was formed at a temperature below 100°C with a higher relative humidity of 90%. The amounts of the respective oxides increased with temperature and relative humidity. In addition, the film thicknesses of tin oxides estimated from the areas of reduction peaks were close agreement with FIB/SEM data. Source


Nakayama S.,Sumitomo Electric Industries | Sugihara T.,Sumitomo Electric Industries | Matsumoto J.,Sumitomo Electric Industries | Notoya T.,Japan Copper and Brass Association | Osakai T.,Kobe University
Journal of the Electrochemical Society | Year: 2011

A new voltammetric method for the determination of corrosion products on tin surfaces has been proposed. In a borate buffer solution, which has frequently been used as the supporting electrolyte for this purpose, no well-separated reduction current peaks for tin oxides were obtained, while in an ammonia buffer solution (0.5 M NH 4OH 0.5 M NH 4Cl), well-defined reduction peaks for anhydrous SnO and hydrated SnO 2 (denoted as SnO 2nH 2O) were observed in a voltammogram. The potentials at these current peaks were separated by ∼0.3 V. Using this suitable electrolyte, we found that the main corrosion products formed on tin in air were SnO and SnO 2nH 2O. These tin oxides were confirmed by X-ray diffraction analysis. It was also found that SnO was formed in air at a temperature higher than 100C, while SnO 2nH 2O was formed at a temperature below 100C and at a higher relative humidity 90. © 2011 The Electrochemical Society. Source


Nakayama S.,Sumitomo Electric Industries | Notoya T.,Japan Copper and Brass Association | Osakai T.,Kobe University
Analytical Sciences | Year: 2012

Until recently, there had been two conflicting views about the order of copper oxides (Cu 2O and CuO) in their cathodic reduction with a neutral or weak alkaline electrolyte (typically 0.1 M KCl). In 2001, we successfully employed a strongly alkaline electrolyte (SAE; i.e., 6 M KOH + 1 M LiOH) to achieve a perfect separation of the reduction peaks of the two oxides. It was then found that the oxides were reduced in SAE according to a thermodynamic order, i.e., " CuO → Cu 2O" , and also that the reduction of CuO occurred in one step. At an extremely slow scan rate of <0.2 mV s -1, however, CuO appears to be reduced in two steps via Cu 2O. It has also been shown that the developed method with SAE can be applied to analysis of various corrosion products, including Cu 2S, Cu(OH) 2, and patinas. Use of the developed method has allowed researchers to clarify the mechanism of the atmospheric corrosion of copper. © 2012 The Japan Society for Analytical Chemistry. Source


Nakayama S.,Sumitomo Electric Industries | Notoya T.,Japan Copper and Brass Association | Osakai T.,Kobe University
Journal of the Electrochemical Society | Year: 2010

A recently developed voltammetric technique using a strongly alkaline electrolyte (6 M KOH+1 M LiOH) was successfully applied to clarify a corrosion mechanism of copper under atmospheric conditions. In contrast to conventional potentiometric methods with neutral or weak alkaline electrolytes (e.g., 0.1 M KCl), the developed method could give qualitative and quantitative information about the corrosion products of copper, including oxides (i.e., Cu2O and CuO) and hydroxide [Cu(OH)2]. In the presence of water under such atmospheric conditions, Cu(OH)2 was the initial corrosion product formed on a copper surface. However, the surface Cu (OH)2 layer did not grow much but dehydrated to become a layer of CuO. The thus-formed CuO layer grew until it became several molecules thick (∼2 nm). For further progress of corrosion, an inner Cu2 O layer was generated by the proportionation reaction between the CuO layer and the base metal Cu. The inner Cu2 O layer grew for the subsequent oxidation until the thickness reached a certain value (∼35 nm). For further oxidation, the top CuO layer grew again preferentially over the inner Cu2 O layer. © 2010 The Electrochemical Society. Source


Itagaki M.,Tokyo University of Science | Ashie N.,TOTO Ltd. | Honda H.,TOTO Ltd. | Hagiwara K.,Kitz Metalworks Corporation | And 2 more authors.
Zairyo to Kankyo/ Corrosion Engineering | Year: 2010

Polarization curves of brass, dezincing-resistant brass and bronze were measured by channel flow double electrode (CFDE), and the electrochemical property of dezincing-resistant brass was investigated. By using CFDE, Cu (I) and Cu (II) ions dissolved from the copper-alloy electrode can be determined simultaneously during the measurement of polarization curve. The anodic polarization curve of brass was divided into two potential regions, namely, selective dissolution of zinc below 0 V vs. SSE (region I) and both dissolutions of copper and zinc above 0 V vs. SSE (region JJ). In the case of anodic polarization curve of dezincing-resistant brass ranked as type I by JBMA T303 test, the current was small in the region I, and the dissolution ratio of zinc was small in the region II. On the other hand, the corrosion test under the fresh water flow was carried out for brass, dezincing-resistant brass, bronze and SUS316. As the result, the dissolution morphology of dezincing-resistant brass ranked as type I tended to general corrosion even in the case that the brass showed the dezincing corrosion. In addition, the short circuit between the dezincing-resistant brass ranked as type I and SUS316 didn't show galvanic corrosion since the corrosion potential of the dezincing-resistant brass ranked as type I is closed to that of SUS316 in the present test water. Source

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