Fig 1.
Electrochemical tests of samples.
(a) Potentiodynamic polarization curves of Fe78Si9B13 glassy ribbons and the corresponding master alloy with different scanning rates ν in 0.6 M NaCl + 0.12 M NaOH solution. For clarity, the curves of Fe78Si9B13 glassy ribbons with ν = ν0, 2 ν0, 3 ν0, 4 ν0, 6 ν0 and 10 ν0 are shifted upward by multiplying the raw data with 102, 104, 106, 108, 1010 and 1012 respectively. (b) Variation of the current densities iP1 and peak potentials EP1 with the square root of ν. (c) Variation of the current densities iP2 and peak potentials EP2 with ν. P1 and P2 indicate the two current density peaks such as A-B-C and C-D-E zones in the polarization curve with ν = 10 ν0 (ν0 = 0.5 mV/s), respectively.
Fig 2.
Potentiodynamic polarization curves of Fe73.5Si13.5B9Cu1Nb3 glassy ribbons and the corresponding master alloy with different scanning rates ν in 0.6 M NaCl + 0.12 M NaOH solution.
For clarity, the curves of Fe73.5Si13.5B9Cu1Nb3 glassy ribbons with ν = 6 ν0, 7 ν0, 8 ν0, 9 ν0 and 10 ν0 are shifted upward by multiplying the raw data with 102, 104, 106, 108 and 1010 respectively.
Fig 3.
Potentiodynamic polarization curves of Fe78Si9B13 glassy ribbons in 0.6 M NaCl + x M NaOH (x = 0.04–0.7) solution with ν = 1mV/s.
For clarity, the curves with c = 0.8 c0, 1.2 c0, 2 c0, 4 c0, 5 c0 and 7 c0 are shifted upward by multiplying the raw data with 102, 104, 106, 108, 1010 and 1012 respectively.
Table 1.
Variation of polarization parameters of Fe78Si9B13 and Fe73.5Si13.5B9Cu1Nb3 glassy ribbons.
Fig 4.
SEM micrographs for the surfaces of (a) and (b) S1, (c) and (d) S2, and (e) and (f) S3 samples.
S1 and S2 were polarized with ν = 2 mV/s until the end of the first and second anodic peaks, respectively, while S3 was polarized to a similar potential to S2 with ν = 1 mV/s after experiencing three corrosion potentials. S1, S2 and S3 are indicated in Fig 1A.
Fig 5.
XPS spectra of (a) Fe 2p and (b) Si 2p recorded from the surfaces of S1, S2 and S3.
S1 and S2 were polarized with ν = 2 mV/s until the end of the first and second anodic peaks, respectively, while S3 was polarized to a similar potential to S2 with ν = 1 mV/s after experiencing three corrosion potentials. S1, S2 and S3 are indicated in Fig 1A.
Table 2.
The fraction of decomposed peaks from XPS spectra for Fe 2p and Si 2p of the surfaces of S1, S2 and S3.
Fig 6.
The schematic of practical cathodic and anodic curve intersection model.
(a) Deducing of imaginary cathodic line from the difference of measured anodic curves; (b) deducing the corrosion potentials of Fe78Si9B13 glassy ribbon with 1 mV/s from that with ν = 5 mV/s in 0.6 M NaCl + 0.12 M NaOH solution by imposing an extrapolated imaginary cathodic line, i.e. moving evenly the imaginary cathodic line; (c) deducing the polarization curve of Fe73.5Si13.5B9Cu1Nb3 glassy ribbon with ν = 7 mV/s from that with ν = 10 mV/s in 0.6 M NaCl + 0.12 M NaOH solution by rotating the imaginary cathodic line; and (d) deducing the polarization curve of Fe78Si9B13 glassy ribbons with cNaOH = 0.12 and 0.08 M from that with 0.7 M by rotating the imaginary cathodic line.
Table 3.
The values of slope and intercept for imaginary cathodic line (ICL) for the anodic and cathodic curve intersection model of of the two samples; solution: 0.6 M NaCl+0.12 M NaOH solution.
Table 4.
The measured and deduced value and
for the two samples; solution: 0.6 M NaCl + 0.12 M NaOH solution.
Table 5.
The values of slope and intercept for imaginary cathodic line (ICL) for the anodic and cathodic curve intersection model of Fe78Si9B13 glassy ribbon; solution: 0.6 M NaCl + x M NaOH.
Table 6.
The measured and deduced value and
for Fe78Si9B13 glassy ribbons; solution: 0.6 M NaCl + 0.12 and 0.08 M NaOH.