Experimental Research on Biomedical Titanium Coating Corrosion Effects

Transcription

1 769 A publcaton of CHEMICAL ENGINEERING TRANSACTIONS VOL. 59, 2017 Guest Edtors: Zhuo Yang, Junje Ba, Jng Pan Copyrght 2017, AIDIC Servz S.r.l. ISBN ; ISSN The Italan Assocaton of Chemcal Engneerng Onlne at DOI: /CET Expermental Research on Bomedcal Ttanum Coatng Corroson Effects Shangq Sun, Xang Lu School of Materals Scence and Engneerng, Kunmng Unversty of Scence and Technology, Kunmng , Chna sunshangq@126.com The NT shape memory alloy sample s subjected to a plasma sprayng technque to form a layer of 400 um thck ttanum coatng on ts surface. The corroson resstance of the samples can be compared by the electrochemcal measurement n the smulated body flud envronment. Thus, the presence of galvanc corroson between the ttanum coatng and the nckel-ttanum shape memory alloy substrate can be measured. The anodc polarzaton curves show that the NT shape memory alloy after ttanum coatng has a decrease n the current densty of the dopant, whle the polarzaton resstance ncreases wth the corroson potental and the passvaton potental. In addton, the galvanc current tme curve shows that the tantalum coatng and nckel-ttanum alloy between the galvanc current densty s mnmal. The experments demonstrate that the surface modfcaton of nckel ttanum shape memory alloy surface coatng can effectvely mprove the corroson resstance of the matrx metal and there s no galvanc corroson between the coatng and the base metal. 1. Introducton In recent years, wth the development of orthopaedc and nterventonal medcne, nckel-ttanum alloys, whch have many advantages, such as ts unque shape memory effect, super-elastcty and good bocompatblty, become one of the mportant bomedcal metal materals. It has been used n the motor system njury, oral orthodontc and cardovascular and cerebrovascular nterventon and other medcal felds n order to mprove the qualty of human lfe (Franks et al., 2005). Although the nckel-ttanum alloy s an excellent mplanted alloy materal, ts corroson resstance and abrason resstance have not yet reached the deal standard. Corroson and wear wll not only reduce the mechancal and mechancal propertes of metal materals, but also the alloy n the hgh nckel, the surroundng tssue wll produce some sde effects, such as senstzaton, carcnogenc reactons (Beltrán-Partda et al., 2017). Therefore, as a bomedcal metal materal wdely used n the human body, the research on the corroson resstance of NT (NTSMA) s of great practcal sgnfcance to ensure ts safe use n the human body (Leng et al., 2003). In recent years, the surface coatng technology has developed rapdly, and t has acheved the purpose of preventng metal corroson and mprovng bocompatblty by formng a protectve coatng on the metal surface (Ye et al., 2014). In ths experment, the ttanum (T) coatng was formed on the NTSMA surface by plasma sprayng technque. The electrochemcal test method of NTSMA before and after coatng s used to smulate the anodc polarzaton curve and characterstc parameters (Campanell et al., 2017). In addton, the corroson resstance of NTSMA before and after the coatng s also nvestgated. The galvanc corroson s nvestgated between the ttanum coatng and the NT alloy substrate accordng to the measurement of the galvanc current-tme curve (Cu et al., 2013). The method of effectvely enhancng the corroson resstance of NTSMA s dscussed n ths paper (Novoa et al., 2017). Bomedcal metal materals are present n the envronment for a long tme, such as n contact wth the body fluds and on the one hand body metal, wll produce corroson of metal materals, whch wll lead to the precptaton of metal ons and ther dervatves and reduce the mechancal strength of the mplanted materal (Zhang et al., 2016). On the other hand, the metal ons wll be generated durng the corroson process longterm exposure to body tssue, whch produce a varety of damage n the body, such as cytotoxcty, allerges, Please cte ths artcle as: Sun Shangq, Lu Xang, 2017, Expermental research on bomedcal ttanum coatng corroson effects, Chemcal Engneerng Transactons, 59, DOI: /CET

2 770 carcnogenc. Therefore, the mprovement of bocompatblty of medcal ttanum alloys s largely dependent on ts mproved corroson resstance. Test methods of corroson resstance of metal materals are dvded nto two knds whch are n vvo and n vtro. Metal corroson resstance n vvo s extremely dffcult for measurement, and the results are dffcult to summarze (Shah et al., 2014). Thus, vtro method s generally used, whch can manly be dvded nto two categores: one for the soakng test can drectly detect the amount of precptaton of ons, but the test cycle s long (De Gopegu, 2010). The other s electrochemcal measurement, whch has fast, senstve and accurate advantages. The electrodynamc polarzaton method s a knd of electrochemcal measurement method. The lnear relatonshp between the appled potental and the current reflects the potental range of the metal to keep the passvaton, the pttng tendency and the ablty of the metal or alloy to reach the steady state n the medum (Huang et al., 2016). Especally t s sutable for low corroson rate of a varety of materals measurement, screenng cted. When the potental polarzaton s scanned, the change n the postve drecton through the anode current electrode s called as the anodc polarzaton (Lu et al., 2006). The curve of the anode current or current densty s the abscssa, and the curve plotted wth the anode potental as the ordnate s called the anodc polarzaton curve (Çelk, 2016). In recent years, the ttanum wth ts stable bologcal characterstcs, good bocompatblty and unque structural propertes of bomedcal ndustry has attracted more and more attentons. Ttanum n the physologcal or other envronment, even n the state of hypoxa, the surface can mmedately generate a layer of chemcal stablty of the passvaton flm, thus the ttanum has excellent chemcal stablty and resstance to physologcal corroson, and has a good bocompatblty (Zhang et al., 2009). In 1940, pure metal ttanum was frst used n medcal care. So far, most cases have reported that there s no adverse reacton of metal ttanum as a human mplant, except that there are 1 case of chronc urtcaral after mplantaton of ttanum nals. Ttanum research and deepenng of clncal research and acheved satsfactory results. Ttanum s expected to become a new generaton of bomedcal metal materals. If the correspondng coatng technology wll be sprayed on the surface of nckel-ttanum alloy and made of medcal materals, the theory of ths materal not only has a good comprehensve mechancal propertes, such as nckel-ttanum alloy matrx, natural bone close to the elastc modulus wth the ncrease of ttanum coatng surface modfcaton treatment, but also make up the nckel-ttanum alloy corroson resstance, wear resstance. The shortcomngs of the dfference wll greatly mprove the bocompatblty of the materal (Burnat et al., 2015). In ths study, T / NTSMA composte samples are prepared by N-ray coatng on NTSMA matrx and tested for corroson resstance. 2. Materals and Method 2.1 Sample matrx materal and sample preparaton The base materal used n ths experment s NTSMA (suppled by Baoj Tanru Nonferrous Metal Materal Co., Ltd.), and the composton s T: 49.3%, N: 51.7%. The samples are cut nto 20mm x 20mmX1.5mm square peces, 24 samples of whch are randomly dvded nto a coatng group and a control group, each group of 12 samples. And the test surface by gold phase sandpaper s step by step grndng (from W40 sandpaper polshed to W10 sandpaper) nto the anhydrous ethanol to save stand-by. Spray coatng tantalum coatng, the coatng group of samples n the vacuum plasma sprayng equpment prepared tantalum coatng, sprayng parameters for the spray dstance of 150mm, coatng thckness of 400 pull m, vacuum chamber pressure 100mm, current 600A, voltage 7V. When the copper wre s welded on the non-test surface of the specmen, t s cured wth epoxy resn and exposed only to the test surface. The test area s 1cm2, and all samples are ultrasoncally cleaned wth absolute ethanol for 10mn before the experment wth dry spare. 2.2 Laboratory equpment and expermental medum DH2080 plasma sprayng equpment (Shangha Rufa sprayng Machnery Co., Ltd.); 351 type electrochemcal corroson test system (the Unted States EC & GPrnceton Appled Research company); CS501-3C constant temperature water bath box (Chongqng four of the Expermental Instrument Co., Ltd.); Scannng Electron Mcroscope (JEOM, Japan). 800ml smulated body flud electrolytc cell wll be flled wth nto the 370C constant temperature water bath box. Smulated body fluds usng Troyde'S type, and ts composton s: NaCl8.0g/L, KCl 0.35/L, NaHCO g/L, KH2PO4, g/l, Na2HP4 1g/L, Glucose 3.57g / L. The electrolyte s not degassed. 2.3 Expermental method and data processng Galvanc corroson s called contact corroson, whch s dfferent metal by dfferent parts of the contact and resultng n galvanc current caused by corroson. The cause of the galvanc current s that the corroson potental of the dssmlar metal s dfferent, whch results n an ncrease or n corroson of the metal wth lower

3 corroson potental. In vvo envronment, metal or alloy mplants nevtably produce varyng degrees of wear wth body tssue such as bone tssue, teeth, etc., whch can lead to loss of metal or alloy surface coatng. So that the coatng metal and the base metal at the same tme are exposed to the nternal envronment, such as n the tssue flud, salva and other electrolytes under the acton of the formaton of the orgnal battery and produce galvanc current. The sze of the galvanc current s manly determned by the self-corroson potental dfference of the par of metals, that s, the greater the dfference between the values of the two metals s, the faster the galvanc corroson rate s. Thus t can affect the qualty of the mplant. In order to scentfcally evaluate the galvanc corroson stuaton, the necessary galvanc experments are only carred out n the smulaton of the body envronment n order to obtan relable conclusons. 771 Fgure 1: Schematc plan of three electrode As seen n Fg.1, the classc three-electrode system s used n corroson test system to saturaton calomel electrode (saturated calomel electrode, SCE) as the reference electrode, and platnum (Pt) electrode s seen as the auxlary electrode. The workng electrode s studed, and measured temperature s controlled at 37. The results of corroson measurement: 1) Anodc polarzaton curve test: NTSMA sample and Ta/NTSMA composte specmen are mmersed n 37 C Troyde S smulated body flud (ph=7.0) n 351 electrochemcal corroson test system, so that the surface tends to be stable. After 30 mnutes, the electrochemcal test software wll be opened. Frstly, the entre ntal delay perod of the open-crcut potental value s shown on the screen, and the value changes wth tme s very small, and then t wll be around a relatve set of ups and downs wth the potental fluctuaton of not more than 2mV effectve. Ths ndcates that the surface condton of the test specmen has been stablzed, and the potental value at ths tme s the self-corroson potental. After the ntal delay, the anodc polarzaton curve s plotted wth an ntal potental of 100 mv (relatve to the selfetchng potental) and a fnal potental of 2000 mv (relatve to the reference electrode) wth a scannng speed of 1 mv / s. each of the coatng group and the control group should repeat sx samples wth 6 polarzaton curves. One of the sx polarzaton curves s selected by software analyss, and the expermental group and the control group are supermposed to compare the polarzaton curve shape of the samples before and after the tantalum coatng. The current densty tests the same electrode system, the auxlary electrode platnum electrode s replaced wth T/NTSMA composte sample, the workng electrode for the NTSMA sample, wre lead H, and then access the same electrode test sde, the second s composed of pars of pars. Snce the data are affected by envronmental and operatonal errors, all data are expressed as mean ± standard devaton (z±s). Usng SPSS11 the statstcal software for completely randomzed desgn data varance analyss and t test wth sgnfcance level a = For the galvanc current tme curve, the scan tme s set to 400s, and then we can measure the even current densty value. Coatng group and the control group of 6 samples are completely random combned to 6 pars. Average value: x N N x Standard devaton: (1)

4 772 s x 2 x N (2) 3. Expermental results The T coatng s successfully prepared on the surface of NTSMA sample by plasma sprayng method, and the T / NTSMA composte sample can be obtaned wth the vsual nspecton of ttanum coatng for the slvergray, no skn, bubblng phenomenon. SEM mcrograph of NT SMA after coatng ttanum s shown n Fg. 2. Ttanum coatng and the matrx n close contact wth the surface are the mcrocrystallne. And the polarzaton curve s a graph whch shows the relatonshp between the electrode potental and the polarzaton current or the polarzaton current densty. Fgure 2: SEM mcrograph of NT SMA after coatng ttanum From the shape of the polarzaton curve, we can see the degree of electrode polarzaton to determne the electrode reacton process.as shown n Fg.3, the anodc polarzaton curve of the NTSMA sample before and after sprayng the T coatng are gven. And the average value of the corroson potental, the dummy current densty (Ip), the polarzaton resstance (Rp), and the passvaton potental (Etp) are also consdered n ths paper. The results show that the corroson potental of NTSMA s ncreased after the T coatng treatment, and the polarzaton resstance and the passvaton potental are ncreased. It can also be seen from Fg. 3 that the passvaton nterval of T / NTSMA complex s obvously longer than that of NTSMA. Fgure 3: Anodc polarzaton curve of NT SMA before and after coatng ttanum

5 Statstcal analyss shows that the values of Ip and Rp of NTSMA samples before and after T coatng are statstcally sgnfcant (P<0.01), and Etp s also dfferent. The tme curve of the galvanc current between the metal coatng and the NT SMA base metal s shown n Fg. 4. The electrc current densty s (1.37±0.14) ua/cm2 (n=6). It can be seen that the galvanc current densty between the tantalum metal coatng and the base nckel-ttanum alloy s stablzed at ua (10-6 A/cm 2 ). 773 Fgure 4: Galvanc current-tme curve of T-NT SMA In ths experment, the anodc polarzaton curves and several mportant electrochemcal parameters of NTSMA coated T coatng are obtaned by ths method: self-corroson potental, dmensonal current densty, polarzaton resstance, over-passvaton potental. T / NTSMA s used to replace the auxlary electrode platnum sheet, and the par of NTSMA s formed. The galvanc current flowng through the alloy electrode s measured under the condton of no voltage appled to the system. It can be seen from Fg.3, even on the current decreases wth tme, the most obvous performance s appeared n the frst 50s, then the current decreases slowly and gradually to be stablzed. And then we measure the current, whch s then dvded by the electrode test area, so you can get the even current densty value. T metal coatng and NTSMA stable after the galvanc current densty value can be mantaned n the ua (10-6 A/cm 2 ) class, whose value s mnmal and no galvanc corroson s occurred. Therefore, ths experment shows that metal ttanum s safe to use as a coatng materal and nckel-ttanum alloy, meanwhle t can mprove the corroson resstance of nckel-ttanum alloy at the same tme, between whch there s no galvanc corroson. 4. Concluson The surface of the NT shape memory alloy can be coated wth a layer of ttanum, whch has a thckness of about 400 um by a plasma spray method. The surface modfcaton treatment can effectvely mprove the corroson resstance of nckel-ttanum shape memory alloy by electrochemcal measurement, and there s no galvanc corroson between them. It s optmzed for N-T shape memory alloy mplant, whch provdes a drecton for development. However, electrochemcal measurement s a short-term, rapd method on the T / NTSMA composte long-term corroson resstance, whch stll need a varety of expermental methods of comprehensve evaluaton. The experments demonstrate that the surface modfcaton of nckel ttanum shape memory alloy surface coatng can effectvely mprove the corroson resstance of the matrx metal and there s no galvanc corroson between the coatng and the base metal. Acknowledgments Ths work was supported by the Natonal Natural Scence Foundaton of Chna (Grant no ). Reference Beltrán-Partda E., Valdéz-Salas B., Moreno-Ulloa A., 2017, Improved n vtro angogenc behavor on anodzed ttanum doxde nanotubes. Journal of nanobotechnology, 15(1), 10, DOI: /s

6 774 Burnat B., Robak J., Batory D., 2015, Surface characterzaton, corroson propertes and boactvty of Cadoped TO 2 coatngs for bomedcal applcatons. Surface and Coatngs Technology, 280, , DOI: /j.surfcoat Campanell L.C., Bortolan C.C., Da Slva P.S.C.P., 2017, Effect of an amorphous ttana nanotubes coatng on the fatgue and corroson behavors of the bomedcal T-6Al-4V and T-6Al-7Nb alloys. Journal of the Mechancal Behavor of Bomedcal Materals, 65, , DOI: /j.jmbbm Cu W.F., Jn L., Zhou L., 2013, Surface characterstcs and electrochemcal corroson behavor of a preanodzed mcroarc oxdaton coatng on ttanum alloy. Materals Scence and Engneerng: C, 33(7), , DOI: /j.msec Çelk İ, 2016, Influence of CrN Coatng on Electrochemcal Behavor of Plasma Ntrded Pure Ttanum n Bosmulated Envronment. Journal of Bonc Engneerng, 13(1), , DOI: /S (14) De Gopegu U.R., Bayón R., Zubzarreta C., 2010, Carbon Contanng Ttanum Coatng for T6Al4V Implants. ECS Transactons, 25(19), 17-32, DOI: / Franks W., Schenker I., Schmutz P., 2005, Impedance characterzaton and modelng of electrodes for bomedcal applcatons. IEEE Transactons on Bomedcal Engneerng, 52(7), , DOI: /TBME Huang Y., Zhang X., Qao H., 2016, Corroson resstance and cytocompatblty studes of znc-doped fluorohydroxyapatte nanocomposte coatngs on ttanum mplant. Ceramcs Internatonal, 42(1), , DOI: /j.ceramnt Leng Y.X., Sun H., Yang P., 2003, T-O/T-N bomedcal gradent flms syntheszed by metal vacuum arc plasma deposton and thermal oxdaton, Plasma Scence, ICOPS IEEE Conference Record- Abstracts. The 30th Internatonal Conference on. IEEE, 281, DOI: /PLASMA Lu C., Ln G., Yang D., 2006, In vtro corroson behavor of multlayered T/TN coatng on bomedcal AISI 316L stanless steel. Surface and Coatngs Technology, 200(12), , DOI: /j.surfcoat Novoa L., Cortes Rodrguez L.E., Gonzales E., Jmenez A., Cortes Ocana L.G., Ojeda Cuello M.D., Barbosa A.L., 2017, Evaluaton of antcorrosve effect of nobum carbde coatng appled on carbon steel, Chemcal Engneerng Transactons, 57, , DOI: /CET Shah A., Izman S., Kadr A., 2014, Influence of Bas Voltage on Corroson Resstance of TN Coated on Bomedcal TZrNb Alloy, Advanced Materals Research. Trans Tech Publcatons, 845, , DOI: / Ye X., Yang Y., Tang G., 2014, Mcrohardness and corroson behavor of surface gradent oxde coatng on the ttanum alloy strps under hgh energy electro-pulsng treatment. Surface and Coatngs Technology, 258, , DOI: /j.surfcoat Zhang D., Zeng W., Z Z., 2009, Corroson resstance of TN coated bomedcal ntnol under deformaton. Materals Scence and Engneerng: C, 29(5), , DOI: /j.msec Zhang X., Wang H., L J., 2016, Corroson behavor of Zn-ncorporated antbacteral TO 2 porous coatng on ttanum. Ceramcs Internatonal, 42(15), , DOI: /j.ceramnt Novoa L., Cortes Rodrguez L.E., Gonzales E., Jmenez A., Cortes Ocana L.G., Ojeda Cuello M.D., Barbosa A.L., 2017, Evaluaton of antcorrosve effect of nobum carbde coatng appled on carbon steel, Chemcal Engneerng Transactons, 57, , DOI: /CET