抄録
The widespread use of tin brass in the condenser tubes may be attributed to its higher corrosion resistance than brass. Tin brass, however, suffers from polluted water corrosion at power stations using polluted water. Its corrosion occurs with sulphur compounds which are released by the action of bacteria. Therefore, potentiostatic measurements of the polarization curve for tin brass including various contents of zinc, tin and iron were carried out stirring 3%NaCl aqueous solution containing 1 ppm cystine.
The results obtained are as follows:
(1) Cystine accelerates the cathodic and anodic reaction rates.
(2) The effect of the zinc content on the electrochemical properties relates linearly to the zinc equivalent. There is a discontinuous change in electrochemical properties due to precipitation of the β phase. Before the precipitation, the cathodic critical current density decreases and anodic current density increases with the zinc equivalent, but after the precipitation, these current increase with the zinc equivalent respectively.
(3) The effect of tin content on electrochemical properties relates to precipitation of the δ phase, below which cathodic critical current decreases and anodic current increases with tin content, but above which the cathodic current does not decrease and the anodic current increases with the tin content.
(4) When the specimens contain iron, the above effects are lessened.
