Figure 1.
Potentiodynamic polarization curves of specimens with different microdefects immersed in uncarbonated simulated pore solution (USPS) (a) and carbonated simulated pore solution (CSPS) (b) for 2 h.
Figure 1.
Potentiodynamic polarization curves of specimens with different microdefects immersed in uncarbonated simulated pore solution (USPS) (a) and carbonated simulated pore solution (CSPS) (b) for 2 h.
Figure 2.
Electrical equivalent circuit used to simulate the electrochemical impedance spectroscopy (EIS) data of defective specimens in stage Ⅰ (a) and stage Ⅱ (b).
Figure 2.
Electrical equivalent circuit used to simulate the electrochemical impedance spectroscopy (EIS) data of defective specimens in stage Ⅰ (a) and stage Ⅱ (b).
Figure 3.
Open circuit potential (OCP)-elapsed time curves of defective specimens in USPS (a) and CSPS (b).
Figure 3.
Open circuit potential (OCP)-elapsed time curves of defective specimens in USPS (a) and CSPS (b).
Figure 4.
Nyquist (a,c) and Bode (b,d) plots of specimens with different defects immersed in USPS (a,b) and CSPS (c,d) for 24 h.
Figure 4.
Nyquist (a,c) and Bode (b,d) plots of specimens with different defects immersed in USPS (a,b) and CSPS (c,d) for 24 h.
Figure 5.
The variation trend of the Ro with the size of the defects in USPS and CSPS for 24 h.
Figure 5.
The variation trend of the Ro with the size of the defects in USPS and CSPS for 24 h.
Figure 6.
Nyquist (a,c) and Bode (b,d) plots of specimens with different defects at corrosion stage Ⅱ in different solutions: USPS (a,b) and CSPS (c,d).
Figure 6.
Nyquist (a,c) and Bode (b,d) plots of specimens with different defects at corrosion stage Ⅱ in different solutions: USPS (a,b) and CSPS (c,d).
Figure 7.
Local electrochemical impedance spectroscopy (LEIS) mappings around the defects of S800 (a), S400 (b), S200 (c), S100 (d) and S50 (e) before being immersed in simulated pore solution (SPS).
Figure 7.
Local electrochemical impedance spectroscopy (LEIS) mappings around the defects of S800 (a), S400 (b), S200 (c), S100 (d) and S50 (e) before being immersed in simulated pore solution (SPS).
Figure 8.
LEIS mappings around the defects of S800 (a1,a2), S400 (b1,b2), S200 (c1,c2), S100 (d1,d2) and S50 (e1,e2) after being immersed in USPS for 24 h (a1–e1) and 84 d (a2–e2).
Figure 8.
LEIS mappings around the defects of S800 (a1,a2), S400 (b1,b2), S200 (c1,c2), S100 (d1,d2) and S50 (e1,e2) after being immersed in USPS for 24 h (a1–e1) and 84 d (a2–e2).
Figure 9.
LEIS mappings around the defects of S800 (a1,a2), S400 (b1,b2), S200 (c1,c2), S100 (d1,d2) and S50 (e1,e2) after being immersed in CSPS for 21 d (a1–e1) and 63 d (a2–e2).
Figure 9.
LEIS mappings around the defects of S800 (a1,a2), S400 (b1,b2), S200 (c1,c2), S100 (d1,d2) and S50 (e1,e2) after being immersed in CSPS for 21 d (a1–e1) and 63 d (a2–e2).
Figure 10.
Scanning vibrating electrode technique (SVET) mappings around the defects of S800 (a), S400 (b), S200 (c), S100 (d) and S50 (e) before being immersed in SPS.
Figure 10.
Scanning vibrating electrode technique (SVET) mappings around the defects of S800 (a), S400 (b), S200 (c), S100 (d) and S50 (e) before being immersed in SPS.
Figure 11.
SVET mappings around the defects of S800 (a), S400 (b), S200 (c), S100 (d) and S50 (e) after being immersed in USPS for 84 d.
Figure 11.
SVET mappings around the defects of S800 (a), S400 (b), S200 (c), S100 (d) and S50 (e) after being immersed in USPS for 84 d.
Figure 12.
SVET mappings around the defects of S800 (a1,a2), S400 (b1,b2), S200 (c1,c2), S100 (d1,d2) and S50 (e1,e2) after being immersed in CSPS for 24 h (a1–e1) and 63 d (a2–e2).
Figure 12.
SVET mappings around the defects of S800 (a1,a2), S400 (b1,b2), S200 (c1,c2), S100 (d1,d2) and S50 (e1,e2) after being immersed in CSPS for 24 h (a1–e1) and 63 d (a2–e2).
Figure 13.
XPS graphs of substrate surface under different conditions: (a) XPS depth etching diagram; (b) XPS spectrum of Fe 2p on surface of specimen before immersed in SPS; (c,d) XPS spectra of Fe 2p on the surface of specimens immersed in USPS and CSPS, respectively, for 24 h.
Figure 13.
XPS graphs of substrate surface under different conditions: (a) XPS depth etching diagram; (b) XPS spectrum of Fe 2p on surface of specimen before immersed in SPS; (c,d) XPS spectra of Fe 2p on the surface of specimens immersed in USPS and CSPS, respectively, for 24 h.
Figure 14.
SEM micrographs of corrosion products under coating after being immersed in USPS for 84 days: (a) S800, (b) S400, (c) S200, (d) S100, (e) S50.
Figure 14.
SEM micrographs of corrosion products under coating after being immersed in USPS for 84 days: (a) S800, (b) S400, (c) S200, (d) S100, (e) S50.
Figure 15.
Ramam spectrum (a) and X-ray diffraction (b) analysis of the rust layer after immersed in USPS for 84 days.
Figure 15.
Ramam spectrum (a) and X-ray diffraction (b) analysis of the rust layer after immersed in USPS for 84 days.
Figure 16.
SEM micrographic cross-sections of defects with metallographs of corrosion products under coating inserted after being immersed in CSPS for 63 days: (a) S800, (b) S400, (c) S200, (d) S100, (e) S50.
Figure 16.
SEM micrographic cross-sections of defects with metallographs of corrosion products under coating inserted after being immersed in CSPS for 63 days: (a) S800, (b) S400, (c) S200, (d) S100, (e) S50.
Figure 17.
Ramam spectrum (a) and X-ray diffraction (b) analysis of the rust layer after being immersed in CSPS for 63 days.
Figure 17.
Ramam spectrum (a) and X-ray diffraction (b) analysis of the rust layer after being immersed in CSPS for 63 days.
Figure 18.
Schematic of the corrosion mechanism when defective specimens were immersed in CSPS (a) and USPS (b).
Figure 18.
Schematic of the corrosion mechanism when defective specimens were immersed in CSPS (a) and USPS (b).
Table 1.
Chemical composition of the reinforcing steel bar used in this study.
Table 1.
Chemical composition of the reinforcing steel bar used in this study.
Element | C | Si | Mn | P | S | Cr | Ni | Cu | V | Fe |
---|
wt.% | 0.22 | 0.43 | 1.25 | 0.017 | 0.02 | 0.03 | 0.02 | 0.02 | 0.035 | Bal |
Table 2.
Abbreviations for the specimens with different sizes of defects.
Table 2.
Abbreviations for the specimens with different sizes of defects.
Diameter of Defect (μm) | 800 | 400 | 200 | 100 | 50 |
Name | S800 | S400 | S200 | S100 | S50 |
Table 3.
Composition and pH of simulated pore solutions.
Table 3.
Composition and pH of simulated pore solutions.
Solution | Concentration (mol/L) | pH |
---|
NaOH | Ca(OH)2 | NaHCO3 | Na2CO3 | NaCl |
---|
USPS | 0.1 | saturated | 0 | 0 | 0.6 | 13.2 |
CSPS | 0 | 0 | 0.06 | 0.04 | 0.6 | 9.8 |
Table 4.
Fitting data of polarization curves.
Table 4.
Fitting data of polarization curves.
Solution | Fitting Data | Specimen |
---|
800 | 400 | 200 | 100 | 50 |
---|
USPS | Ecorr (V) | −0.368 | −0.261 | −0.183 | −0.161 | −0.149 |
Icorr (A/cm2) | 7.74 × 10−10 | 3.22 × 10−10 | 9.546 × 10−11 | 1.07 × 10−10 | 9.31× 10−11 |
CSPS | Ecorr (V) | −0.488 | −0.437 | −0.379 | −0.349 | −0.169 |
Icorr (A/cm2) | 1.06× 10−7 | 9.39 × 10−8 | 3.24 × 10−9 | 3.89 × 10−10 | 1.17 × 10−10 |
Table 5.
Overview of the defect and periphery impedance obtained in LEIS experiments.
Table 5.
Overview of the defect and periphery impedance obtained in LEIS experiments.
| S800 | S400 | S200 | S100 | S50 |
---|
| Impedance (Ohm) |
---|
USPS | 0 h | defect | 1.05 × 105 | 0.90 × 105 | 0.99 × 105 | 1.17 × 105 | 0.96 × 105 |
periphery | 1.14 × 105 | 1.32 × 105 | 1.53 × 105 | 1.31 × 105 | 1.04 × 105 |
24 h | defect | 1.00 × 106 | 0.74 × 106 | 1.60 × 106 | 3.10 × 106 | 4.40 × 106 |
periphery | 8.56 × 106 | 5.40 × 106 | 1.07 × 107 | 2.83 × 107 | 2.57 × 107 |
84 days | defect | 1.21 × 106 | 1.08 × 106 | 1.24 × 106 | 1.21 × 106 | 1.22 × 106 |
periphery | 1.64 × 106 | 1.33 × 106 | 1.63 × 106 | 1.54 × 106 | 1.40 × 106 |
CSPS | 0 h | defect | 1.05 × 105 | 0.90 × 105 | 0.99 × 105 | 1.17 × 105 | 0.96 × 105 |
periphery | 1.14 × 105 | 1.32 × 105 | 1.53 × 105 | 1.31 × 105 | 1.04 × 105 |
21 days | defect | 3.21 × 105 | 5.34 × 105 | 3.28 × 105 | 4.49 × 105 | 4.88 × 105 |
periphery | 4.04 × 105 | 6.97 × 105 | 4.43 × 105 | 8.23 × 105 | 1.11 × 106 |
63 days | defect | 1.47 × 106 | 1.30 × 106 | 1.38 × 106 | 1.65 × 106 | 1.30 × 106 |
periphery | 1.81 × 106 | 1.73 × 106 | 1.78 × 106 | 2.03 × 106 | 1.77 × 106 |
Table 6.
Overview of the defect current density obtained in SVET experiments.
Table 6.
Overview of the defect current density obtained in SVET experiments.
| | S800 | S400 | S200 | S100 | S50 |
---|
| | Current Density (μA/cm2) |
---|
USPS | 0 h | 23.0 | 20.7 | 20.7 | 17.0 | 3.76 |
84 d | 0.24 | 0.22 | 0.21 | 0.090 | −0.015~0.045 |
CSPS | 0 h | 23.0 | 20.7 | 20.7 | 17.0 | 3.76 |
21 d | 14.9 | 12.4 | 16.8 | 13.4 | 4.20 |
63 d | 0.676 | 0.530 | 0.466 | 0.444 | −0.041~0.027 |