Corrosion and electrochemical characterization of rapidly solidified CuB, CuAlB, CuCrZr alloys

Abstract

The effect of pH and chloride ions on the corrosion and related electrochemical properties of the microcrystalline, rapidly solidified copper alloys with a small content of boron, aluminium, chromium and zirconium as alloying elements were studied. The pH of solutions has an apparent impact on the corrosion behaviour of the investigated alloys. At a low pH value corrosion of the alloys can be considered as a dissolution with soluble products. In neutral and alkaline solutions the presence of oxides, built up on the surface of the alloys, has a significant effect at the corrosion potential. In the neutral solution the presence of oxides results in higher polarization resistances of the alloys. Relatively low polarization resistance values of most of the alloys in the alkaline solution are most likely due to the growth of a porous Cu 2O film which does not hinder further dissolution. The chloride ions visibly influence the formation of the surface layers and anodic dissolution processes during polarization. After 45 min of immersion their effect on the polarization resistance is negligible. The potentiodynamic polarization curves of the CuB 3, CuAl 5B 6 and CuAl 1B 12 alloys display similar features in acidic, alkaline and chloride solutions. Their behaviour in alkaline and chloride solutions while polarizing is mostly determined by the properties of copper. The behaviour of the CuCr 4Zr 3 alloys display similar features in acidic, alkaline and the alloying elements. The alloying elements, in the quantity used in the investigated alloys, have certain effect on the corrosion resistances in acidic and alkaline solutions. In the alkaline solution the alloy with chromium and zirconium shows apparently higher polarization resistance. In the acidic solution alloying elements lower the polarization resistance values. In neutral solutions CuAl 5B 6 displays highest polarization resistance.