Effect of Zinc and Aluminium on Corrosion of Aluminium Brass by Polluted Water

A reason for the widespread use of aluminium brass in heat exchanger tubes may be attributed to its high corrosion and erosion resistance. Aluminium brass, however, suffer from a polluted water corrosion at power station using a polluted sea water. Its corrosion occures with sulpher compounds which are released by the action of bacteria. Therefore, the potentiostatic measurements of polarization curve for aluminium brass including various contents of zinc and aluminium were carried out in slowly stirring 3%NaCl aqueous solution containing 1 p.p.m. cystine.The results obtained were as follows:(1) Mainly, cystine accelerates cathodic reaction rate, its effect is remarkable esspecially in absence of oxygen.(2) Although effects of zinc and aluminium contents on electrochemical properties relate linearly to zinc equivalent, there is a discontinuous point at about 32%Zn eq., below which cathodic critical current decreases with zinc equivalent and anodic current increases with either of decrease of aluminium content or increase of zinc content, but above which these currents increase with zinc equivalent respectively.(3) There are some relation between these discontinuous points and precipitation of β phase.