An electrochemical, topographical and analytical study on the behaviour of the metal-metalloid glass (Fe, Cr)80 (P, C, Si)20 in chloride or sulfate containing aqueous solutions

The metal-metalloid glass (Fe, Cr)(80) (P, C, Si)(20) was investigated in aqueous solutions which contain high quantities of NaCl (3 M). For comparison we use a solution with 1.5 M Na2SO4. These solutions reach from the strong acid area (0.5 M H2SO4) to the strong alkaline region (1 M NaOH). The corrosive properties of the metal-metalloid glass were determined at 25 degrees C and 50 degrees C. By the use of electrochemical methods it was possible to estimate the long time corrosive properties. Therefore current-potential-curves were determined by the use of a potentiodynamic technique. Starting from this curves it was possible by use of the tafel plot method or the determination of the polarisation resistance to calculate an annual pull down of the metallic glass. For these electrochemical experiments we used the glass ribbons as electrodes and we measured under rotating conditions. The determined values of the annual pull down vary in a large region. The highest rate (44 mm/a) was calculated for an acid chloride containing solution at a temperature of 50 degrees C. The lowest pull down rate (approximate to 0.3 mu m/a) is obtained in the alkaline solution at room temperature. In the alkaline area there is no difference between the addition of NaCl or Na2SO4. The treated glass fibres were characterised by the use of Scanning Electron Microscopy (SEM) and EDX-Analysis.