Research On The Corrosion Resistance Of Aluminum Brass With Trace Cr, Co

ABSTRACT:In the current industry, adding arsenic is the normal method to improve the corrosion resistance of brass alloys.However the arsenic as a kind of highly toxic element, not only has polluted the environment seriously, but also would bring great harm to human health. Therefore, we need to find an alloy element one can improve the brass alloy corrosion resistance and will not pollute the environment.A series of brass alloys, were prepared by smelting and rolling in this thesis. The microstructure, mechanical properties and corrosion resistance of brass alloys has been evaluated with the help of optical microscope, X-ray diffraction instrument, scanning electron microscope, electron probe micro analyzer, electron diffraction spectrometer, electronic universal testing machine and electrochemical workstation. Besides, the microstructure and the properties of the brass alloys as a function of the addition amount of chromium or cobalt were also investigated. The conclusions are as follows:(1) Exhibited in the brass alloys as CuCrx phase; Chromium could constrain the growth of the brass alloys grains effectively. Also, Chromium could remarkably improve mechanical properties of the brass alloys by the second phase strengthening. Furthermore, the corrosion resistance of the brass alloys was enhanced by adding chromium due to the presence of passivation membrane on the alloys surfaces.(2) Chromium could reduce the corrosion rate of the brass alloys in the3.5%NaCl solution. It was observed that the corrosion products of the brass alloys in3.5%NaCl solution were (Cu,Zn)2Cl(OH)3and CuCl2-3Cu(OH)2, as some small granular particles distributed on the alloy surface, acted as a protective layer and suppressed the further penetration of NaCl solution, thereby effectively improved the corrossion resistance. When the chromium content is0.65wt%, the brass alloys showed the excellent corrosion resistance.(3) Chromium could promote the corrosion rate of the brass alloys in the3.5%NaCl+0.5mol/LNH4Cl solution. The corrosion products of the brass alloys in the3.5%NaCl+0.5mol/LNH4Cl solution are Cu (OH) Cl and Cu (OH)2NH3H2O, as sheet-like microstructure attached to the alloy surface, and have no protective effect to the brass alloys.(4) Cobalt could obviously refine brass alloy grain and improve the microhardness of the brass alloy. In addition, cobalt could reduce the corrosion rate of the brass alloys in the3.5%NaCl solution and the3.5%NaCl+0.5mol/LNH4Cl solution.(5) When the colbat content is0.4wt%, the brass alloys showed the excellent corrosion resistance.With further increasing the cobalt content, the corrosion resistance of the brass alloys would be reduced due to the excess cobalt prompt K phase grow up and the alloy organization coarsened.