Use of CeO₂ nanoparticles as CO₂-corrosion inhibitors of a duplex stainless steel

Figures & data

Figure 1. X-ray patterns of CeO₂ NPs.

Figure 2. (a) SEM and (b)TEM micrographs of CeO₂ NPs.

Figure 3. Effect of the CeO₂ NPs concentration on the OCP value for LDX 2101 duplex stainless steel in a CO₂-saturated 3.5% NaCl solution.

Figure 4. Effect of the CeO₂ NPs concentration on the polarization curves for LDX 2101 duplex stainless steel in a CO₂-saturated 3.5% NaCl solution.

Table 1. Electrochemical parameters obtained from polarization curves.

CeO2 conc. (ppm)	Ecorr (mV)	Icorr (mA/cm^2)	Epit (mV)	βa (mV/dec)	βc (mV/dec)	I.E. (%)	θ
0	−770	3 × 10^−2	−375	125	−330	–	–
200	−730	8 × 10^−3	−280	115	−310	73	0.73
400	−680	5 × 10^−3	−270	100	−305	83	0.83
600	−520	2 × 10^−4	0	80	−290	99	0.99
800	−630	3 × 10^−3	−260	90	−280	93	0.93

Figure 5. Langmuir adsorption isotherm for LDX 2101 duplex stainless steel in a CO₂-saturated 3.5% NaCl solution containing CeO₂ NPs.

Figure 6. Effect of the CeO₂ NPs concentration on the R_p value for LDX 2101 duplex stainless steel in a CO₂-saturated 3.5% NaCl solution.

Figure 7. (a) Nyquist and (b) Bode diagrams for LDX 2101 duplex stainless steel in uninhibited CO₂–saturated 3.5% NaCl solution.

Figure 8. (a) Nyquist and (b) Bode diagrams for LDX 2101 duplex stainless steel in CO₂-saturated 3.5% NaCl solution containing 600 ppm of CeO₂ NPs.

Figure 9. Electric circuit to simulate the EIS data.

Table 2. Electrochemical parameters obtained from fitting the EIS data for uninhibited solution.

Time (h)	Rs (ohm cm^2)	CPEdl (F/cm^2)	ndl	Rct (ohm cm^2)	CPEf (F/cm^2)	nf	Rf (ohm cm^2)
0	4.9	4.88 × 10^−4	0.7	341	4.69 × 10^−4	0.8	1015
3	4.8	4.60 × 10^−4	0.7	455	3.19 × 10^−4	0.8	1605
6	4.8	4.20 × 10^−4	0.7	614	2.98 × 10^−4	0.9	1630
9	4.8	4.03 × 10^−4	0.7	687	2.87 × 10^−4	0.9	1738
12	5.0	3.66 × 10^−4	0.7	724	2.00 × 10^−4	0.9	2516
18	4.9	3.44 × 10^−4	0.7	755	2.22 × 10^−4	0.9	3272
24	5.2	2.88 × 10^−4	0.7	836	1.20 × 10^−4	0.9	4363

Table 3. Electrochemical parameters obtained from fitting the EIS data for tests containing 600 ppm of CeO₂ NPs.

Time (h)	Rs (ohm cm^2)	CPEdl (F/cm^2)	ndl	Rct (ohm cm^2)	CPEf (F/cm^2)	nf	Rf (ohm cm^2)
0	3.6	3.02 × 10^−4	0.7	6	3.41 × 10^−4	0.7	1117
3	5.7	8.84 × 10^−5	0.9	8	8.78 × 10^−5	0.8	95,020
6	5.5	4.83 × 10^−5	0.9	16	3.05 × 10^−5	0.9	180,240
9	5.5	4.59 × 10^−5	0.9	17	2.94 × 10^−5	0.9	131,860
12	5.2	4.88 × 10^−5	0.9	18	2.83 × 10^−5	0.9	133,860
18	5.8	4.16 × 10^−5	0.9	19	2.69 × 10^−5	0.9	134,070
24	5.8	3.77 × 10^−5	0.9	20	8.61 × 10^−6	0.9	160,070

Figure 10. SEM micrographs of LDX 2101 duplex stainless steel corroded in a CO₂-saturated 3.5% NaCl solution containing (a) 0, (b) 200, (c) 400, (d) 600 and (e) 800 ppm of CeO₂ NPs.

Figure 11. Raman spectrum of pure CeO₂ NPs and LDX 2101 duplex stainless steel corroded in a CO₂-saturated 3.5% NaCl solution containing 600 and 800 ppm of CeO₂ NPs.

Data availability statement

The raw/processed data required to reproduce these findings are available upon request.