Understanding the role of alloyed Ni and Cu on improving corrosion resistance of low alloy steel in the simulated Beishan groundwater

doi:10.1016/j.jmst.2022.03.037

Abstract

Abstract:

The corrosion behavior of NiCu low alloy steel and Q235 low carbon steel as the candidate materials for geological disposal containers of high-level radioactive waste in the simulated Beishan groundwater was comparatively studied by weight loss test, electrochemical measurements, scanning electron microscope (SEM), electron probe microanalysis (EPMA), X-ray diffraction (XRD), Raman spectrum and X-ray photoelectron spectroscopy (XPS). The electrochemical results showed that the corrosion potential of NiCu steel and Q235 steel gradually increased with the immersion time. Simultaneously, the cathodic process transited from hydrogen evolution reaction (HER) control to the rust reduction control, while the anodic process was always dominated by the active dissolution of iron. By comparison, both the cathodic resistance and the anodic dissolution resistance of NiCu steel corrosion were apparently higher than that of Q235 steel. The results of rust layer characterization indicated that Ni and Cu elements could be enriched in the inner rust layer of NiCu steel and the rust layer was more compact. As the main corrosion products, the content of α-FeOOH in the rust layer of NiCu steel was obviously increased more than that of Q235 steel. Fe₆(OH)₁₂SO₄ stably existed in the corrosion products of NiCu steel because Ni(II) or Cu(II) could substitute Fe(II) of Fe₆(OH)₁₂SO₄ and increased its oxidation resistance. Moreover, Ni and Cu could also make Fe₃O₄ ionic selective by doping. After the long-term immersion, the corrosion mass loss of NiCu steel was significantly lower than Q235 steel, which further confirmed the benefits of Ni and Cu alloying on improving the steel corrosion resistance.

Key words: Deep geological disposal, Container material, Groundwater, Corrosion behavior, Electrochemical measurement

Yupeng Sun, Xin Wei, Junhua Dong, Nan Chen, Hanyu Zhao, Qiying Ren, Wei Ke. Understanding the role of alloyed Ni and Cu on improving corrosion resistance of low alloy steel in the simulated Beishan groundwater[J]. J. Mater. Sci. Technol., 2022, 130: 124-135.

Figures/Tables 14

References 80

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Coupons	C	Si	Mn	P	S	Cu	Ni	Fe
Q235	0.21	0.21	0.58	0.017	0.036	0.02	-	Balance
NiCu	0.06	0.51	0.61	0.009	0.002	0.47	3.29	Balance

Coupons	C	Si	Mn	P	S	Cu	Ni	Fe
Q235	0.21	0.21	0.58	0.017	0.036	0.02	-	Balance
NiCu	0.06	0.51	0.61	0.009	0.002	0.47	3.29	Balance

No.	Electrode reaction	Equilibrium potential equation (vs. SCE)	E (V vs. SCE)
2	2H⁺ + 2e → H₂	E = −0.2438 - 0.05916 pH - 0.02958 lgP_H2	−0.7260
3	2Fe + 2H₂O + HCO₃⁻ → Fe₂(OH)₂CO₃ + 3H⁺ + 4e	E = −0.5220 - 0.04437 pH - 0.01479 lg[HCO₃⁻]	−0.8422
4	6Fe + 12H₂O + HCO₃⁻ → Fe₆(OH)₁₂CO₃ + 13H⁺+ 14e	E = −0.4021 - 0.05493 pH - 0.004226 lg[HCO₃⁻]	−0.8379
5	6Fe + 12H₂O + SO₄²⁻ → Fe₆(OH)₁₂SO₄ + 13H⁺ + 14e	E = −0.3955 - 0.5071 pH - 0.004226 lg[SO₄²⁻]	−0.7996
6	Fe + 2H₂O → α-FeOOH + 3H⁺ + 3e	E = −0.2658 - 0.05916 pH	−0.7480
7	Fe + 2H₂O → γ-FeOOH + 3H⁺ + 3e	E = −0.2315 - 0.05916 pH	−0.7136
8	3Fe + 4H₂O → Fe₃O₄ + 8H⁺ + 8e	E = −0.3304 - 0.05916 pH	−0.8126
9	Fe + 2H₂O → Fe(OH)₂ + 2H⁺ + 2e	E = −0.3072 - 0.05916 pH	−0.7893
10	Fe(OH)₂ →α-FeOOH + H⁺ + e	E = −0.1830 - 0.05916 pH	−0.6652
11	Fe(OH)₂ →γ-FeOOH + H⁺ + e	E = −0.0801 - 0.05916 pH	−0.5622
12	3α-FeOOH + H⁺ + e → Fe₃O₄ + 2H₂O	E = 0.2511 - 0.05916 pH	−0.2310
13	3γ-FeOOH + H⁺ + e → Fe₃O₄ + 2H₂O	E = 0.5599 - 0.05916 pH	0.0778
14	8α-FeOOH + Fe³⁺ + 3e → 3Fe₃O₄ + 4H₂O	E = 0.2569 + 0.01972 lg[Fe³⁺]	0.1583
15	8γ-FeOOH + Fe³⁺ + 3e → 3Fe₃O₄ + 4H₂O	E = 0.5314 + 0.01972 lg[Fe³⁺]	0.4328
16	8α-FeOOH + Fe²⁺ + 2e → 3Fe₃O₄ + 4H₂O	E = 0.1227 + 0.02958 lg[Fe³⁺]	−0.0252
17	8γ-FeOOH + Fe²⁺ + 2e → 3Fe₃O₄ + 4H₂O	E = 0.5345 + 0.02958 lg[Fe³⁺]	0.3866
18	5α-FeOOH + Fe³⁺ + HCO₃⁻ + 2H₂O + 2H⁺ + 4e → Fe₆(OH)₁₂CO₃	E = 0.2153 - 0.02958 pH + 0.01479 lg[HCO₃⁻] + 0.01479 lg[Fe³⁺]	−0.1411
19	5γ-FeOOH + Fe³⁺ + HCO₃⁻ + 2H₂O + 2H⁺ + 4e → Fe₆(OH)₁₂CO₃	E = 0.3350 - 0.02958 pH + 0.01479 lg[HCO₃⁻] + 0.01479 lg[Fe³⁺]	−0.0125
20	5α-FeOOH + Fe²⁺ + HCO₃⁻ + 2H₂O + 2H⁺ + 3e → Fe₆(OH)₁₂CO₃	E = 0.1121 - 0.03944 pH + 0.01972 lg[HCO₃⁻] + 0.01972 lg[Fe²⁺]	−0.3632
21	5γ-FeOOH + Fe²⁺ + HCO₃⁻ + 2H₂O + 2H⁺ + 3e → Fe₆(OH)₁₂CO₃	E = 0.2836 - 0.03944 pH + 0.01972 lg[HCO₃⁻] + 0.01972 lg[Fe²⁺]	−0.1917
22	5α-FeOOH + Fe³⁺ + SO₄²⁻ + 2H₂O + 3H⁺ + 4e → Fe₆(OH)₁₂SO₄	E = 0.1923 - 0.04437 pH + 0.01479 lg[SO₄²⁻] + 0.01479 lg[Fe³⁺]	−0.2755
23	5γ-FeOOH + Fe³⁺ + SO₄²⁻ + 2H₂O + 3H⁺ + 4e → Fe₆(OH)₁₂SO₄	E = 0.3210 - 0.04437 pH + 0.01479 lg[SO₄²⁻] + 0.01479 lg[Fe³⁺]	−0.1468
24	5α-FeOOH + Fe²⁺ + SO₄²⁻ + 2H₂O + 3H⁺ + 3e → Fe₆(OH)₁₂SO₄	E = 0.0814 - 0.05916 pH + 0.01972 lg[SO₄²⁻] + 0.01972 lg[Fe³⁺]	−0.5424
25	5γ-FeOOH + Fe²⁺ + SO₄²⁻ + 2H₂O + 3H⁺ + 3e → Fe₆(OH)₁₂SO₄	E = 0.2530 - 0.05916 pH + 0.01972 lg[SO₄²⁻] + 0.01972 lg[Fe³⁺]	−0.3708
26	6α-FeOOH + HCO₃⁻ + 5H⁺ + 4e → Fe₆(OH)₁₂CO₃	E = 0.1696 - 0.07395 pH + 0.01479 lg[HCO₃⁻]	−0.4331
27	6γ-FeOOH + HCO₃⁻ + 5H⁺ + 4e → Fe₆₍OH)₁₂CO₃	E = 0.3653 - 0.07395 pH + 0.01479 lg[HCO₃⁻]	−0.2787
28	6α-FeOOH + SO₄²⁻+ 6H⁺+ 4e → Fe₆(OH)₁₂SO₄	E = 0.1880 - 0.08874 pH + 0.01479 lg[SO₄²⁻]	−0.5675
29	6γ-FeOOH + SO₄²⁻+ 6H⁺+ 4e → Fe₆(OH)₁₂SO₄	E = 0.3424 - 0.08874 pH + 0.01479 lg[SO₄²⁻]	−0.4131

No.	Electrode reaction	Equilibrium potential equation (vs. SCE)	E (V vs. SCE)
2	2H⁺ + 2e → H₂	E = −0.2438 - 0.05916 pH - 0.02958 lgP_H2	−0.7260
3	2Fe + 2H₂O + HCO₃⁻ → Fe₂(OH)₂CO₃ + 3H⁺ + 4e	E = −0.5220 - 0.04437 pH - 0.01479 lg[HCO₃⁻]	−0.8422
4	6Fe + 12H₂O + HCO₃⁻ → Fe₆(OH)₁₂CO₃ + 13H⁺+ 14e	E = −0.4021 - 0.05493 pH - 0.004226 lg[HCO₃⁻]	−0.8379
5	6Fe + 12H₂O + SO₄²⁻ → Fe₆(OH)₁₂SO₄ + 13H⁺ + 14e	E = −0.3955 - 0.5071 pH - 0.004226 lg[SO₄²⁻]	−0.7996
6	Fe + 2H₂O → α-FeOOH + 3H⁺ + 3e	E = −0.2658 - 0.05916 pH	−0.7480
7	Fe + 2H₂O → γ-FeOOH + 3H⁺ + 3e	E = −0.2315 - 0.05916 pH	−0.7136
8	3Fe + 4H₂O → Fe₃O₄ + 8H⁺ + 8e	E = −0.3304 - 0.05916 pH	−0.8126
9	Fe + 2H₂O → Fe(OH)₂ + 2H⁺ + 2e	E = −0.3072 - 0.05916 pH	−0.7893
10	Fe(OH)₂ →α-FeOOH + H⁺ + e	E = −0.1830 - 0.05916 pH	−0.6652
11	Fe(OH)₂ →γ-FeOOH + H⁺ + e	E = −0.0801 - 0.05916 pH	−0.5622
12	3α-FeOOH + H⁺ + e → Fe₃O₄ + 2H₂O	E = 0.2511 - 0.05916 pH	−0.2310
13	3γ-FeOOH + H⁺ + e → Fe₃O₄ + 2H₂O	E = 0.5599 - 0.05916 pH	0.0778
14	8α-FeOOH + Fe³⁺ + 3e → 3Fe₃O₄ + 4H₂O	E = 0.2569 + 0.01972 lg[Fe³⁺]	0.1583
15	8γ-FeOOH + Fe³⁺ + 3e → 3Fe₃O₄ + 4H₂O	E = 0.5314 + 0.01972 lg[Fe³⁺]	0.4328
16	8α-FeOOH + Fe²⁺ + 2e → 3Fe₃O₄ + 4H₂O	E = 0.1227 + 0.02958 lg[Fe³⁺]	−0.0252
17	8γ-FeOOH + Fe²⁺ + 2e → 3Fe₃O₄ + 4H₂O	E = 0.5345 + 0.02958 lg[Fe³⁺]	0.3866
18	5α-FeOOH + Fe³⁺ + HCO₃⁻ + 2H₂O + 2H⁺ + 4e → Fe₆(OH)₁₂CO₃	E = 0.2153 - 0.02958 pH + 0.01479 lg[HCO₃⁻] + 0.01479 lg[Fe³⁺]	−0.1411
19	5γ-FeOOH + Fe³⁺ + HCO₃⁻ + 2H₂O + 2H⁺ + 4e → Fe₆(OH)₁₂CO₃	E = 0.3350 - 0.02958 pH + 0.01479 lg[HCO₃⁻] + 0.01479 lg[Fe³⁺]	−0.0125
20	5α-FeOOH + Fe²⁺ + HCO₃⁻ + 2H₂O + 2H⁺ + 3e → Fe₆(OH)₁₂CO₃	E = 0.1121 - 0.03944 pH + 0.01972 lg[HCO₃⁻] + 0.01972 lg[Fe²⁺]	−0.3632
21	5γ-FeOOH + Fe²⁺ + HCO₃⁻ + 2H₂O + 2H⁺ + 3e → Fe₆(OH)₁₂CO₃	E = 0.2836 - 0.03944 pH + 0.01972 lg[HCO₃⁻] + 0.01972 lg[Fe²⁺]	−0.1917
22	5α-FeOOH + Fe³⁺ + SO₄²⁻ + 2H₂O + 3H⁺ + 4e → Fe₆(OH)₁₂SO₄	E = 0.1923 - 0.04437 pH + 0.01479 lg[SO₄²⁻] + 0.01479 lg[Fe³⁺]	−0.2755
23	5γ-FeOOH + Fe³⁺ + SO₄²⁻ + 2H₂O + 3H⁺ + 4e → Fe₆(OH)₁₂SO₄	E = 0.3210 - 0.04437 pH + 0.01479 lg[SO₄²⁻] + 0.01479 lg[Fe³⁺]	−0.1468
24	5α-FeOOH + Fe²⁺ + SO₄²⁻ + 2H₂O + 3H⁺ + 3e → Fe₆(OH)₁₂SO₄	E = 0.0814 - 0.05916 pH + 0.01972 lg[SO₄²⁻] + 0.01972 lg[Fe³⁺]	−0.5424
25	5γ-FeOOH + Fe²⁺ + SO₄²⁻ + 2H₂O + 3H⁺ + 3e → Fe₆(OH)₁₂SO₄	E = 0.2530 - 0.05916 pH + 0.01972 lg[SO₄²⁻] + 0.01972 lg[Fe³⁺]	−0.3708
26	6α-FeOOH + HCO₃⁻ + 5H⁺ + 4e → Fe₆(OH)₁₂CO₃	E = 0.1696 - 0.07395 pH + 0.01479 lg[HCO₃⁻]	−0.4331
27	6γ-FeOOH + HCO₃⁻ + 5H⁺ + 4e → Fe₆₍OH)₁₂CO₃	E = 0.3653 - 0.07395 pH + 0.01479 lg[HCO₃⁻]	−0.2787
28	6α-FeOOH + SO₄²⁻+ 6H⁺+ 4e → Fe₆(OH)₁₂SO₄	E = 0.1880 - 0.08874 pH + 0.01479 lg[SO₄²⁻]	−0.5675
29	6γ-FeOOH + SO₄²⁻+ 6H⁺+ 4e → Fe₆(OH)₁₂SO₄	E = 0.3424 - 0.08874 pH + 0.01479 lg[SO₄²⁻]	−0.4131

Time (day)	R_s (Ω cm²)	Y_0-c (mS sⁿ cm⁻²)	n_c	R_c (Ω cm²)	Y_0-a (mS sⁿ cm⁻²)	n_a	R_a (Ω cm²)
4	62.74	2.539	0.6719	590.6	0.6662	0.7229	1085
10	66.42	5.103	0.6652	625.0	0.6715	0.7615	1069
17	64.95	6.546	0.6833	778.0	0.6229	0.7934	1123
34	68.85	1.385	0.7078	739.3	0.6911	0.9247	974.1
50	68.64	1.923	0.6854	889.1	0.7473	0.9394	1128
65	60.55	1.813	0.7184	951.2	1.006	0.9206	1460
80	63.35	1.398	0.7995	1124	0.7469	1.000	1839
100	62.72	2.464	0.7405	1059	1.003	0.8640	1833
120	55.01	1.702	0.7436	1239	1.309	0.9280	1864