Preparation And Property Of Cu-Zn Alloy For Water Treatment Of Boiler

The chemical composition, melting and moulding technics, as well as properties of Cu-Zn alloys for water treatment of boiler were studied in this work. Three Cu-Zn alloys were prepared, using Cu, Zn, Sn, Ni and microelement RE as raw materials. The effects of alloys on the water quality and anti-scaling property in simulating water circulation system, and the relationship between surface free energy of alloy and its anti-scaling property were studied. Also the polarization curves were mensurated.The cast structures of Cu-Zn alloys for water treatment of boiler were all dendrite. After annealing at 600℃to 800℃, alloy structure became homogeneous, accompanying decreased hardness, enhanced corrosion resistance, and prolonged operating life. Study indicated that the higher surface free energy and the bigger proportion of polarity component were, the better anti-scaling property of the alloy was.The electrode potentials of different elements in Cu-Zn alloys for water treatment of boiler were different, which could form micro-electric-fields. When the water passing by the alloy, scale-forming and corrosive matters were dissociated to cations and anions, then the electrons were absorbed by earthing system. The absorbed electrons were supplied to Ca²⁺ and Mg²⁺ etc., so that they could be able to reach stable state, which avoided to form scale.The electrode potential of Zn was the lowest, and its chemical property was the most activated, so that Zn dissolved during primary reactions, and was oxidized into Zn²⁺. Zn²⁺ could impede the nucleation of calcite, be absorbed on the surface of calcite CaCO₃, and replace partial Ca thereinto, then make the calcite crystal detorted, and form a sosoloid admixture of Zn and Ca, so that it could prevent the scale forming finally.