金メッキを施した7-3黄銅の多硫化アンモニウム水溶液による腐食について
1962 年 11 巻 3 号 p. 106-108
詳細
1962 年 11 巻 3 号 p. 106-108
In the earliest stage-within 72hr at 25°C-of corrosion of Zn, Cu, 7-3 brass and their gold-plated specimens by 5% ammonium polysulphide aq. solution, various corrosion products were observed by using X-ray back reflection and electron transmission diffraction method. On corrosion of zinc, ZnO, αZnS and ZnSO4⋅3Zn(OH)2⋅4H2O were formed contacting with the surface of zinc matrix. In the case of copper, Cu9-xS5 alone was detected and corrosion products of 7-3 brass consisted of mixture of CuS, Cu2S and Cu9-xS5 without any compound of zinc.
And moreover, corrosion products formed on the gold-plated specimens of Cu, Zn and 7-3 brass had the same crystallographic forms as the non-gold-plated ones, but the amount of corrosion products of the former is less than the latter. Comparing to corrosion mechanism of such metals and alloys by NaCl aq. solution1), it is concluded that corrosion in weak electrolyte such as aq. solution of ammonium polysulphide doesn't behave galvanic mainly but as normal solid reaction.
