Unveiling the Contribution of Lactic Acid to the Passivation Behavior of Ti-6Al-4V Fabricated by Laser Powder Bed Fusion in Hank’s Solution

doi:10.1007/s40195-023-01602-y

Abstract

Abstract:

In actual physiological environments, bacteria can activate the immune system and release lactic acid. However, the detailed contribution of lactic acid to the passivation behavior of titanium (Ti) alloys is still unclear. The current work investigated the in vitro passivation behavior of Ti-6Al-4V (TC4) alloys fabricated by laser powder bed fusion in Hank's solution with and without adding lactic acid. Electrochemical methods, inductively coupled plasma atomic emission spectrometer, and X-ray photoelectron spectroscopy were jointly used. Adding lactic acid decreases the corrosion resistance of samples by degrading the formed passive film. The film formed in the (lactic acid)-containing solution exhibits a higher level of oxygen vacancies and a lower thickness, attributed to the suppressed formation of Ti⁴⁺ transformed from Ti³⁺ and Ti²⁺. Moreover, the presence of lactic acid would increase the open circuit potential, relieve the ions release, and hinder the deposition of calcium phosphates within 24 h immersion.

Key words: Titanium alloy, Corrosion behavior, Passive film, Lactic acid, Laser powder bed fusion

Yu-Hang Chu, Liang-Yu Chen, Bo-Yuan Qin, Wenbin Gao, Fanmin Shang, Hong-Yu Yang, Lina Zhang, Peng Qin, Lai-Chang Zhang. Unveiling the Contribution of Lactic Acid to the Passivation Behavior of Ti-6Al-4V Fabricated by Laser Powder Bed Fusion in Hank’s Solution[J]. Acta Metallurgica Sinica (English Letters), 2024, 37(1): 102-118.

Figures/Tables 17

Fig. 1 Microstructural features of L-PBF-produced TC4 sample: a XRD pattern, b optical microstructure, c bright-field TEM image, d dark-field TEM image (inset is the selected area diffraction pattern in the dashed circle)

Fig. 2 OCP curves of L-PBF-produced TC4 in Hank′s solutions at 37 °C with different pH values controlled by lactic acid. Ti7, Ti5, and Ti3 indicate the samples in Hank′s solutions with pH values of 7, 5 and 3

Fig. 3 Electrochemical impedance spectroscopies of L-PBF-produced TC4 samples in Hank’s solutions with different lactic acid concentrations at 37 °C: a Nyquist plots, b Bode plots. Inset in a is the equivalent electrical circuit fitting the EIS results. Ti7, Ti5, and Ti3 indicate the samples in Hank′s solutions with pH values of 7, 5, and 3

Table 1 Fitting results of electrochemical impedance spectroscopies for L-PBF-produced TC4 in Hank′s solutions with and without lactic acid

Sample	R_s (Ω cm²)	CPE × 10⁻⁶ (Ω⁻¹ sⁿ cm⁻²)	n	R_ct (MΩ cm²)
Ti7	21.07 ± 1.83	29.38 ± 1.93	0.90 ± 0.02	1.07 ± 0.24
Ti5	20.94 ± 1.75	27.56 ± 2.87	0.88 ± 0.02	0.75 ± 0.15
Ti3	18.18 ± 1.89	23.98 ± 2.32	0.90 ± 0.01	0.22 ± 0.14

Fig. 4 Potentiodynamic polarization curves of L-PBF-produced TC4 samples in Hank’s solutions with different lactic acid concentrations at 37 °C. Ti7, Ti5, and Ti3 indicate the samples in Hank′s solutions with pH values of 7, 5 and 3

Table 2 Fitted potentiodynamic polarization results of Ti7, Ti5 and Ti3 samples in Hank’s solution at 37 ℃

Sample	I_corr (µA cm⁻²)	E_corr (V)	E_pp (V)	Corrosion rate × 10⁻⁵ (mm y⁻¹)
Ti7	0.12 ± 0.02	− 0.49 ± 0.06	− 0.043 ± 0.05	0.33 ± 0.11
Ti5	0.15 ± 0.03	− 0.37 ± 0.06	0.081 ± 0.07	0.43 ± 0.14
Ti3	0.18 ± 0.03	− 0.29 ± 0.08	0.139 ± 0.06	0.49 ± 0.16

Fig. 5 Potentiostatic polarization curves and corresponding double logarithmic curves from 0.6 to 1 V: a, b Ti7, c, d Ti5 and e, f Ti3. Insets are enlarged images from 1500 to 1800 s. Ti7, Ti5 and Ti3 indicate the samples in Hank′s solutions with pH values of 7, 5 and 3

Fig. 6 Electrochemical impedance spectroscopy for the L-PBF-produced TC4 after potentiostatic polarization with different pH values at 37 °C: a, c and e Nyquist diagram, b, d and f Bode diagram. Ti7, Ti5 and Ti3 indicate the samples in Hank’s solutions with pH values of 7, 5 and 3

Table 3 Summarized fitting EDS results from Fig. 6

Sample	Potential	R_s	CPE₁ × 10⁻⁶	n₁	R_f	CPE₂ × 10⁻⁵	n₂	R_ct
Sample	(V)	(Ω cm²)	(Ω⁻¹ sⁿ cm⁻²)	n₁	(kΩ cm²)	(Ω⁻¹ sⁿ cm⁻²)	n₂	(MΩ cm²)
Ti7	0.6	20.15 ± 0.84	10.95 ± 0.53	0.90 ± 0.03	10.21 ± 0.62	1.05 ± 0.49	0.76 ± 0.12	1.16 ± 0.12
	0.7	21.02 ± 1.05	4.44 ± 0.71	0.96 ± 0.02	12.39 ± 0.57	5.12 ± 0.53	0.86 ± 0.09	1.92 ± 0.28
	0.8	19.02 ± 1.59	8.62 ± 0.05	0.86 ± 0.08	13.66 ± 0.74	1.56 ± 0.82	0.97 ± 0.01	2.23 ± 0.35
	0.9	23.34 ± 0.83	2.52 ± 0.26	0.72 ± 0.13	20.57 ± 0.35	5.05 ± 0.07	0.96 ± 0.01	2.46 ± 0.76
	1.0	22.81 ± 2.84	1.19 ± 0.08	0.73 ± 0.07	25.23 ± 0.28	6.37 ± 0.79	0.94 ± 0.02	2.81 ± 0.69
Ti5	0.6	16.38 ± 0.24	1.13 ± 0.45	0.91 ± 0.04	5.48 ± 0.43	2.85 ± 0.63	0.93 ± 0.03	1.06 ± 0.35
	0.7	13.21 ± 1.52	2.51 ± 0.37	0.73 ± 0.15	8.68 ± 0.62	8.75 ± 0.49	0.92 ± 0.04	1.41 ± 0.29
	0.8	14.55 ± 1.03	1.83 ± 0.79	0.76 ± 0.12	9.20 ± 0.84	7.82 ± 0.73	0.93 ± 0.03	1.75 ± 0.17
	0.9	13.49 ± 2.26	2.26 ± 0.93	0.77 ± 0.07	11.72 ± 0.38	6.67 ± 0.39	0.94 ± 0.02	2.38 ± 0.44
	1.0	15.84 ± 0.63	3.55 ± 1.04	0.83 ± 0.11	15.24 ± 0.21	4.16 ± 0.27	0.96 ± 0.01	2.73 ± 0.55
Ti3	0.6	14.76 ± 0.14	4.01 ± 1.43	0.64 ± 0.07	9.32 ± 0.46	5.14 ± 0.23	0.92 ± 0.02	0.91 ± 0.20
	0.7	12.29 ± 0.46	3.57 ± 0.74	0.70 ± 0.06	10.21 ± 0.73	9.31 ± 0.53	0.93 ± 0.05	1.15 ± 0.32
	0.8	10.68 ± 0.96	1.98 ± 0.69	0.73 ± 0.04	12.36 ± 0.26	8.08 ± 0.39	0.94 ± 0.03	1.59 ± 0.27
	0.9	11.84 ± 1.65	2.10 ± 1.26	0.73 ± 0.02	13.51 ± 0.07	6.29 ± 0.58	0.94 ± 0.01	1.81 ± 0.17
	1.0	15.4 ± 2.53	8.89 ± 0.37	0.92 ± 0.14	16.32 ± 0.49	4.87 ± 0.74	0.89 ± 0.08	2.42 ± 0.52

Table 3 Summarized fitting EDS results from Fig. 6

Sample	Potential	R_s	CPE₁ × 10⁻⁶	n₁	R_f	CPE₂ × 10⁻⁵	n₂	R_ct
Sample	(V)	(Ω cm²)	(Ω⁻¹ sⁿ cm⁻²)	n₁	(kΩ cm²)	(Ω⁻¹ sⁿ cm⁻²)	n₂	(MΩ cm²)
Ti7	0.6	20.15 ± 0.84	10.95 ± 0.53	0.90 ± 0.03	10.21 ± 0.62	1.05 ± 0.49	0.76 ± 0.12	1.16 ± 0.12
	0.7	21.02 ± 1.05	4.44 ± 0.71	0.96 ± 0.02	12.39 ± 0.57	5.12 ± 0.53	0.86 ± 0.09	1.92 ± 0.28
	0.8	19.02 ± 1.59	8.62 ± 0.05	0.86 ± 0.08	13.66 ± 0.74	1.56 ± 0.82	0.97 ± 0.01	2.23 ± 0.35
	0.9	23.34 ± 0.83	2.52 ± 0.26	0.72 ± 0.13	20.57 ± 0.35	5.05 ± 0.07	0.96 ± 0.01	2.46 ± 0.76
	1.0	22.81 ± 2.84	1.19 ± 0.08	0.73 ± 0.07	25.23 ± 0.28	6.37 ± 0.79	0.94 ± 0.02	2.81 ± 0.69
Ti5	0.6	16.38 ± 0.24	1.13 ± 0.45	0.91 ± 0.04	5.48 ± 0.43	2.85 ± 0.63	0.93 ± 0.03	1.06 ± 0.35
	0.7	13.21 ± 1.52	2.51 ± 0.37	0.73 ± 0.15	8.68 ± 0.62	8.75 ± 0.49	0.92 ± 0.04	1.41 ± 0.29
	0.8	14.55 ± 1.03	1.83 ± 0.79	0.76 ± 0.12	9.20 ± 0.84	7.82 ± 0.73	0.93 ± 0.03	1.75 ± 0.17
	0.9	13.49 ± 2.26	2.26 ± 0.93	0.77 ± 0.07	11.72 ± 0.38	6.67 ± 0.39	0.94 ± 0.02	2.38 ± 0.44
	1.0	15.84 ± 0.63	3.55 ± 1.04	0.83 ± 0.11	15.24 ± 0.21	4.16 ± 0.27	0.96 ± 0.01	2.73 ± 0.55
Ti3	0.6	14.76 ± 0.14	4.01 ± 1.43	0.64 ± 0.07	9.32 ± 0.46	5.14 ± 0.23	0.92 ± 0.02	0.91 ± 0.20
	0.7	12.29 ± 0.46	3.57 ± 0.74	0.70 ± 0.06	10.21 ± 0.73	9.31 ± 0.53	0.93 ± 0.05	1.15 ± 0.32
	0.8	10.68 ± 0.96	1.98 ± 0.69	0.73 ± 0.04	12.36 ± 0.26	8.08 ± 0.39	0.94 ± 0.03	1.59 ± 0.27
	0.9	11.84 ± 1.65	2.10 ± 1.26	0.73 ± 0.02	13.51 ± 0.07	6.29 ± 0.58	0.94 ± 0.01	1.81 ± 0.17
	1.0	15.4 ± 2.53	8.89 ± 0.37	0.92 ± 0.14	16.32 ± 0.49	4.87 ± 0.74	0.89 ± 0.08	2.42 ± 0.52

Fig. 7 Mott-Schottky curves of passive films on samples under different concentrations of lactic acid: a Ti7, b Ti5, c Ti3. Ti7, Ti5 and Ti3 indicate the samples in Hank’s solutions with pH values of 7, 5, 3

Fig. 8 Semiconductive properties of passive films on Ti7, Ti5 and Ti3 after potentiostatic polarization at 0.6-1 V: a donor densities, b thicknesses. Ti7, Ti5 and Ti3 indicate the samples in Hank’s solutions with pH values of 7, 5, 3

Fig. 9 Concentrations of Ti, Al, V, Ca and P ions from potentiostatic polarized samples under 0.6 V and 24 h immersion tests in Hank’s solution: a Ti, Al and V, b Ca and P. Ti7, Ti5 and Ti3 indicate the samples in Hank′s solutions with pH values of 7, 5 and 3

Fig. 10 Morphologies of potentiostatic polarized samples under 0.6 V and 24 h immersion tests: a Ti7, b Ti5, c Ti3. Ti7, Ti5 and Ti3 indicate the samples in Hank′s solutions with pH values of 7, 5 and 3

Table 4 Chemical compositions of feature positions marked in Fig. 10 (in at.%)

Feature position	Ti	Al	V	O
A	82.9	5.1	3.8	8.2
B	84.0	5.2	3.5	7.3
C	83.3	5.4	4	7.3
D	85.2	5.0	3.7	6.1

Fig. 11 Elemental fractions in the passive films at different durations: a Ti7, b Ti5, c Ti3 after potentiostatic polarization under 0.6 V. Ti7, Ti5 and Ti3 indicate the samples in Hank’s solutions with pH values of 7, 5 and 3

Fig. 12 Deconvolved XPS spectra of Ti 2p region for the samples after potentiostatic polarization under 0.6 V in Hank’s solution with the pH value of 7, 5 and 3, respectively. Ti7, Ti5 and Ti3 indicate the samples in Hank’s solutions with pH values of 7, 5 and 3

Fig. 13 Proportions of titanium ions with varying valence in the passive films on the samples after potentiostatic polarization under 0.6 V in Hank′s solution with the pH value of 7, 5 and 3 at different sputtering durations. Ti7, Ti5 and Ti3 indicate the samples in Hank′s solutions with pH values of 7, 5 and 3

References 58

[1]	P. Qin, L.Y. Chen, C.H. Zhao, Y.J. Liu, C.D. Cao, H. Sun, L.C. Zhang, Corros. Sci. 189, 109609 (2021)
[2]	S. Qin, X. Xu, Y. Lu, L. Li, T. Huang, J. Lin, Acta Metall. Sin. -Engl. Lett. 35, 812 (2022)
[3]	L.C. Zhang, L.Y. Chen, Adv. Eng. Mater. 21, 801215 (2019)
[4]	S.B. Sun, L.J. Zheng, J.H. Liu, H. Zhang, Rare Met. 42, 1353 (2023)
[5]	P. Qin, Y. Liu, T.B. Sercombe, Y. Li, C. Zhang, C. Cao, H. Sun, L.C. Zhang, A.C.S. Biomater, Sci. Eng. 4, 2633 (2018)
[6]	C. Xu, L.Y. Chen, C. Zheng, Z.Y. Zhang, R. Li, H.Y. Yang, J. Peng, L. Zhang, L.C. Zhang, Adv. Eng. Mater. 24, 2200674 (2022)
[7]	L.Y. Chen, S.X. Liang, Y. Liu, L.C. Zhang, Mater. Sci. Eng. R Rep. 146, 100648 (2021)
[8]	X.N. Hao, X. Liu, Rare Met. 41, 3677 (2022)
[9]	C. Xu, Y. Peng, L.Y. Chen, T.Y. Zhang, S. He, K.H. Wang, Corros. Sci. 215, 111048 (2023)
[10]	X. Jin, P. Ye, H. Ji, Z. Suo, B. Wei, X. Li, W. Fang, Int. J. Miner. Metall. Mater. 29, 2232 (2022)
[11]	D.C. Rodrigues, P. Valderrama, T.G. Wilson, K. Palmer, A. Thomas, S. Sridhar, A. Adapalli, M. Burbano, C. Wadhwani, Materials 6, 5258 (2013)
[12]	Z. Guo, X. Shen, F. Liu, J. Guan, Y. Zhang, F. Dong, Y. Wang, X. Yuan, B. Wang, L. Luo, Y. Su, J. Cheng, J. Alloys Compd. 960, 170739 (2023)
[13]	J.C.M. Souza, K. Apaza-Bedoya, C.A.M. Benfatti, F.S. Silva, B. Henriques,Metals 10, 1272 (2020)
[14]	L.Y. Chen, H.Y. Zhang, C. Zheng, H.Y. Yang, P. Qin, C. Zhao, S. Lu, S.X. Liang, L. Chai, L.C. Zhang, Mater. Des. 208, 109907 (2021)
[15]	Y.W. Cui, L.Y. Chen, P. Qin, R. Li, Q. Zang, J. Peng, L. Zhang, S. Lu, L. Wang, L.C. Zhang, Corros. Sci. 203, 110333 (2022)
[16]	M. Cabrini, A. Carrozza, S. Lorenzi, T. Pastore, C. Testa, D. Manfredi, P. Fino, F. Scenini, J. Mater. Process. Technol. 308, 117730 (2022)
[17]	P.A. Mashimo, Y. Yamamoto, M. Nakamura, H.S. Reynolds, R.J. Genco, J. Periodont. 56, 548 (1985)
[18]	P.D. Marsh, Adv. Dent. Res. 8, 263 (1994)
[19]	M.A. Houle, D. Grenier, Med. Mal. Infect. 33, 331 (2003)
[20]	G. Mabilleau, S. Bourdon, M.L. Joly-Guillou, R. Filmon, M.F. Basle, D. Chappard, Acta Biomater. 2, 121 (2006)
[21]	L. Benea, N. Simionescu-Bogatu,Materials 14, 7404 (2021)
[22]	A. Banu, L. Preda, M. Marcu, L.L. Dinca, M.E. Maxim, G. Dobri, Metal. Mater. Trans. A 53, 2060 (2022)
[23]	Q. Qu, L. Wang, Y. Chen, L. Li, Y. He, Z. Ding, Materials 7, 5528 (2014)
[24]	H. Mirzadeh, Int. J. Miner. Metall. Mater. 30, 1278 (2023)
[25]	S. Liu, Y.C. Shin, Mater. Des. 164, 107552 (2019)
[26]	W. Xu, M. Brandt, S. Sun, J. Elambasseril, Q. Liu, K. Latham, K. Xia, M. Qian, Acta Mater. 85, 74 (2015)
[27]	H.Y. Yang, Z. Wang, L.Y. Chen, S.L. Shu, F. Qiu, L.C. Zhang, Compos. Part B: Eng. 209, 108605 (2021)
[28]	L.C. Zhang, H. Attar, Adv. Eng. Mater. 18, 463 (2016)
[29]	L. Chen, J. Li, Y. Zhang, W. Lu, L.C. Zhang, L. Wang, D. Zhang, J. Nucl. Sci. Technol. 53, 496 (2016)
[30]	Y. Bai, X. Gai, S. Li, L.C. Zhang, Y. Liu, Y. Hao, X. Zhang, R. Yang, Y. Gao, Corros. Sci. 123, 289 (2017)
[31]	N. Dai, L.C. Zhang, J. Zhang, Q. Chen, M. Wu, Corros. Sci. 102, 484 (2016)
[32]	C. Man, C. Dong, T. Liu, D. Kong, D. Wang, X. Li, Appl. Surf. Sci. 467, 193 (2019)
[33]	C. Man, C. Dong, Z. Cui, K. Xiao, Q. Yu, X. Li, Appl. Surf. Sci. 427, 763 (2018)
[34]	P. Sang, L.Y. Chen, C. Zhao, Z.-X. Wang, H. Wang, S. Lu, D. Song, J.H. Xu, L.C. Zhang, Metals 9, 1342 (2019)
[35]	Y. Xu, M.Y. Tan, Corros. Sci. 151, 163 (2019)
[36]	D.S. Kong, J.X. Wu, J. Electro. Soc. 155, C32 (2008)
[37]	X. Gai, Y. Bai, J. Li, S. Li, W. Hou, Y. Hao, X. Zhang, R. Yang, R.D.K. Misra, Corros. Sci. 145, 80 (2018)
[38]	M. Lakatos-Varsanyi, F. Falkenberg, I. Olefjord, Electrochim. Acta 43, 187 (1998)
[39]	N. Dai, L.C. Zhang, J. Zhang, X. Zhang, Q. Ni, Y. Chen, M. Wu, C. Yang, Corros. Sci. 111, 703 (2016)
[40]	R. Chelariu, G. Bolat, J. Izquierdo, D. Mareci, D.M. Gordin, T. Gloriant, R.M. Souto, Electrochim. Acta 137, 280 (2014)
[41]	G. Bolat, D. Mareci, R. Chelariu, J. Izquierdo, S. Gonzalez, R.M. Souto, Electrochim. Acta 113, 470 (2013)
[42]	D.D. Macdonald, Electrochim. Acta 56, 1761 (2011)
[43]	R.M. Fernandez-Domene, E. Blasco-Tamarit, D.M. Garcia-Garcia, J. Garcia-Anton, Electrochim. Acta 95, 1 (2013)
[44]	Z. Duan, C. Man, C. Dong, Z. Cui, D. Kong, L. Wang, X. Wang, Corros. Sci. 167, 108520 (2020)
[45]	P. Qin, L.Y. Chen, Y.J. Liu, Z. Jia, S.X. Liang, C.H. Zhao, H. Sun, L.C. Zhang, Corros. Sci. 191, 109728 (2021)
[46]	T. Hanawa, Mater. Sci. Eng. C 24, 745 (2004)
[47]	R. Azadbakht, T. Almasi, H. Keypour, M. Rezaeivala, Inorg. Chem. Com. 33, 63 (2013)
[48]	Y.W. Cui, L.Y. Chen, Y.H. Chu, L. Zhang, R. Li, S. Lu, L. Wang, L.C. Zhang, Corros. Sci. 215, 111017 (2023)
[49]	L. Chen, J. Li, Y. Zhang, L.C. Zhang, W. Lu, L. Zhang, L. Wang, D. Zhang, Corros. Sci. 100, 651 (2015)
[50]	L. Guan, Y. Li, G. Wang, Y. Zhang, L.C. Zhang, Electrochim. Acta 285, 172 (2018)
[51]	L.C. Zhang, L.Y. Chen, L. Wang, Adv. Eng. Mater. 22, 1901258 (2020)
[52]	T. Hanawa, M. Ota, Appl. Surf. Sci. 55, 269 (1992)
[53]	L. Zhang, L.Y. Chen, C. Zhao, Y. Liu, L.C. Zhang, Metals 9, 850 (2019)
[54]	Z. Jiang, X. Dai, T. Norby, H. Middleton, Corros. Sci. 53, 815 (2011)
[55]	Z.R. Ye, Z.C. Qiu, Z.B. Wang, Y.G. Zheng, R. Yi, X. Zhou, Acta Metall. Sin. (Engl. Lett.) 33, 839 (2020)
[56]	C. Liu, Y. Li, X. Cheng, X. Li, Acta Metall. Sin. (Engl. Lett.) 35, 1055 (2022)
[57]	Y. Cui, L. Chen, L. Wang, J. Cheng, L. Zhang, Metals 13, 415 (2023)
[58]	O.E.M., Pohler, Injury 31, D7 (2000)