純水中で生ずる銅の腐食生成物

抄録

Microphotographic study of corrosion products of copper in pure water were conducted. And some mechanisms and conditions of yielding corrosion products were discussed.
Corrosion tests were carried out using corrosion test loops at the temperature range of 40-90°C.
As the result, corrosion products were classified as follows:
(1) Yellow coloured acicular corrosion products.
(2) Yellow corrosion products as loam.
(3) Red and violet corrosion products.
(4) Black corrosion products.
By X-ray diffraction and reflectance spectra, predominant component of yellow and red corrosion products was identified with Cu₂O, and that of black corrosion products was CuO.
Mechanisms and conditions of yielding each corrosion products are supposed as follows:
(1) Yellow corrosion products (Cu₂O) are produced by decomposition of CuO under the condition where partial pressure of oxygen is very low and water is rather alkaline.
Acicular crystals grow out of black corrosion products (CuO) which exist under acicular crystals. In detail, CuO dissolve once in water surrounding it, and deposit acicular crystals (Cu₂O), like growth of ice needles, by reduction.
Yellow loam-like corrosion products are formed by direct decomposition of CuO in solid state.
(2) Iced corrosion products (Cu₂O) are yielded under the conditions where water is slightly acidic and/or partial pressure of oxygen is extremely low. These corrosion products have the tendency to peeloff.
(3) Black corrosion products.
Black loam-like corrosion products whose shape is same as yellow one, hemispherical corrosion products and others were observed.
These are produced under the high oxygen partial pressure generally. Hemisperical corrosion productsand loam-like corrosion products are produced at low temperature, low water velocity and high temperature, high velocity respectively. It seems that black loam-like corrosion products and yellow one change into each other easily with the change of conditions.