钛合金经酸碱两步预处理快速沉积HA涂层

目的钛合金经酸碱两步预处理后在表面快速沉积羟基磷灰石涂层。方法钛合金(Ti_6Al_4V)均分为A、B两组。A组先用砂纸打磨,再用0．6mol/L NaOH在160℃下处理24h;B组先用H_2SO_4与HCl混合酸腐蚀1h,再用0．6mol/L NaOH在160℃处理24h。两组试件各8片分别置于过饱和钙磷溶液SCS1- SCS8中24h。XRD和SEM分析涂层成分、表面和断面形貌。表面形貌仪分析沉积前样品的表面粗糙度。结果在SCS1溶液中的钛合金片表面均沉积了致密的羟基磷灰石涂层,涂层表面由片状晶体组成,涂层厚度约为30μm。结论B组样品避免了对试样的打磨,在合适的SCS溶液中同样可以快速沉积羟基磷灰石涂层。该工艺特别适合在复杂形状的样品表面沉积涂层。     

不同碱热处理方法对钛表面理化性能及细胞响应特性的影响

目的对骨科常用钛植入材料进行表面处理,赋予其高生物活性。方法利用酸碱腐蚀法对钛基体进行粗化与活化处理,并通过模拟体液浸泡样品,在钛表面制备了含钙、磷的生物活性无机涂层。通过腐蚀率测定、静滴接触角、SEM等方法研究了粗化及活化处理对钛合金样品表面能、润湿性、粗糙度、表面形貌等理化性能的影响;通过MG63细胞培养实验观察了不同表面处理方法对细胞粘附、分化和增殖情况的影响;并通过SEM、XRD等检测方法对不同方法处理样品在模拟体液中浸泡3天后表面形成的含钙磷沉积层进行观察和分析。结果浸泡后样品表面形成的无机沉积层成分为羟基磷灰石(HA),而且采用HCl/H2SO4混合酸于60℃下处理30分钟、5M NaOH 60℃腐蚀24小时并在600℃下保温1小时的酸碱热处理工艺所得到的钛表面粗糙度高,润湿性好,细胞在其上粘附、分化、增殖情况最佳,且其表面沉积的HA层更为致密均匀。结论通过对钛基体表面酸碱热处理工艺条件进行优化筛选,为后期生物学评价提供初步的实验依据和前期基础。     

预处理方法对等离子体喷涂氧化钛涂层装载庆大霉素的影响研究*

目的 本文研究不同预处理方法对等离子体喷涂氧化钛涂层表面庆大霉素的装载量及缓释性能的影响.方法 采用大气等离子体喷涂设备在钛合金上制备氧化钛涂层,采用酸碱等化学处理手段预处理涂层,然后在涂层表面嫁接固定庆大霉素,光学显微镜观察胶原在涂层表面的分布情况,采用邻苯二甲醛方法检测释放液中含有的庆大霉素量.结果 经1M硫酸或10M氢氧化钠处理后,涂层表面抗菌药物装载量、稳定性皆有明显提高.庆大霉素的胶原溶液比其水溶液更利于其在氧化钛涂层表面的装载.结论 酸或者碱处理皆能明显提高涂层表面抗菌药物的装载量及稳定性.这是由于预处理后形成的Ti-OH与胶原形成分子中存在的-COOH、-NH2、-OH等官能团反应,从而将胶原固定在涂层表面所致.     

仿生法制备纯镁/羟基磷灰石复合涂层的研究

通过酸碱两步法活化纯镁基体表面，用CaCl2和K2HPO4溶液对其进行预钙化处理，将处理过的纯镁试样浸泡于模拟体液中，仿生沉积得到羟基磷灰石涂层。利用X射线衍射和扫描电子显微镜对形成的涂层进行表征。试验结果表明，4周后可在镁基体表面得到了均匀致密、结晶良好的羽毛状羟基磷灰石涂层。     

多孔纯钛种植体表面快速沉积钙磷涂层的研究

商业纯钛片经磨平、喷砂、清洗、酸洗后分成A、B两组。A组不作任何处理,B组用H2SO4和HCl混合液酸蚀,然后两组钛片同时置于37℃的仿生液SBF-A中1d及SBF-B中2d。结果两组钛片表面均可沉积磷灰石涂层,涂层为多孔片状结构,X射线衍射分析证实其为碳酸化羟基磷灰石和磷酸八钙的混合物,钙磷原子量比约1.51。这说明在多孔纯钛表面可以快速仿生沉积碳酸化磷灰石涂层。     

含氟纳米氟磷灰石糊剂修复人工釉质缺损

背景：纳米氟磷灰石糊剂涂敷法可在人牙齿表面生长出类似牙釉质的柱状晶体。 目的：观察1 mg/L人体安全浓度的氟离子对纳米氟磷灰石糊剂修复人工釉质缺损的影响。 方法：将人工早期釉质缺损样本随机分成两组,分别在样本表面涂敷添加含氟的纳米氟磷灰石糊剂(实验组)与不加氟的纳米氟磷灰石糊剂(对照组),置于37 ℃水浴孵箱中修复。反应前后对牙齿表面行扫描电镜观察,晶体结构分析,化学成分鉴定和韦氏显微硬度测试。 结果与结论：经处理后,两组样品表面都可见有一层与牙釉质化学组成和晶体结构类似的晶体生成,但实验组牙釉质样品表面结晶度、韦氏显微硬度明显高于对照组样品(P < 0.05),且实验组牙釉质样品表面更光滑。结果表明,人体安全浓度含氟纳米氟磷灰石糊剂可明显提高人工釉质龋显微硬度、结晶度和表面光滑度。     

严重烧伤病人休克期酸碱失衡类型初探

目的探讨严重烧伤病人在休克期(伤后1-3d)发生酸碱失衡类型的变化,分析其发生的原因与机理.方法随机抽取72例严重烧伤病人(烧伤面积50%-97%,平均72%±18%,三度面积16%-85%,平均38%±22%),用含肝素的注射器采集患者的股动脉血作血气分析,同时用不含抗凝剂的注射器采集患者的股静脉血作电解质测定,两个标本同时送检,同步检测.利用酸碱失衡的四步判断法(见烧伤患者高氯性三重酸碱失衡的判断及其机理的探讨.中国病理生理杂志,2000,16(8)744-748)对同步血气与电解质的检测结果进行判定.结果全组患者除6例酸碱失衡类型属正常外,其余66例中,单纯性酸碱失衡类型28例,双重性23例,三重性15例.在单纯性酸碱失衡类型中,以代谢性酸中毒(代酸)最多,共14例,其余依次为呼吸性碱中毒(呼碱)12例,呼吸性酸中毒(呼酸)2例.在双重性酸碱失衡类型中,则以呼碱并代酸为主,共ll例,其余依次为呼酸并代酸5例,代酸并代碱3例,呼碱并代碱2例,呼酸并代碱与混合性代酸均为l例.在三重性酸碱失衡(TABD)类型中,以呼碱并代酸并代碱多见,共13例,而呼酸并代酸并代碱较少,共2例.其中,以高AG代酸的TABD为主,共12例,高Cl-代酸的TABD比较少,只有3例.此外,代酸、呼碱并代酸、呼酸并代酸、代酸并代碱和高AG性TABD的AG值的升高有高度显著性(P＜0.01).讨论(1)烧伤早期大量的体液丢失引起低血容量性休克,组织乏氧代谢增加,大量酸根离子堆积而导致高AG代酸.如果大量输注等张NaCl溶液(如生理盐水),使血中Na+、Cl-浓度同当量增加,血Cl-浓度显著增加,从而使HCO-3浓度相应降低而发生高Cl-性代酸.(2)烧伤患者因精神紧张、疼痛刺激使呼吸深快、通气过度而发生呼碱;当伴有吸入性损伤或发生呼吸衰竭时,肺通气不畅,CO2潴留导致呼酸.(3)临床上为纠正代酸不适当应用碱性药物(如NaHCO3),易矫枉过正,引起代碱与混合性酸碱失衡.结论严重烧伤患者休克期的酸碱失衡类型非常复杂,几乎包括了各种类型的酸碱失衡,以代谢性酸中毒、呼碱并代酸以及呼碱并代酸并代碱为主,其中的代酸主要为高AG代酸,三重性酸碱失衡并不少见.     

热化学法制备CaTiO3涂层及涂层的生物相容性

背景：钛酸钙(CaTiO₃)作为一种有前途的涂层,可应用于钛基医用植入体表面。 目的：通过一种简单的热化学处理技术,在Ti6Al4V基体上制备均匀的CaTiO₃涂层,同时通过培养成骨细胞观察涂层生物相容性。 方法：通过将Ti6Al4V基体埋于无水硝酸钙(Ca(NO₃)₂)粉末中,并且升高温度;当温度处在Ca(NO₃)2熔点以上时,在Ti6Al4V基体上能够生成一层均匀的CaTiO₃层。同时在热化学处理温度为570 ℃的Ti6Al4V基体材料上进行成骨细胞培养,观察所制备涂层的生物相容性。 结果与结论：该涂层转化只有在(Ca(NO₃)₂)熔点(561 ℃)以上时才会发生,同时随着处理温度的升高,CaTiO₃晶体尺寸随之增大;经过热化学处理后的样品具有良好的生物相容性,对成骨细胞黏附、增殖具有更好的促进作用。该方法简单、有效,所制备的涂层具有良好的生物相容性,有望在钛植入体表面处理中获得应用,以提高金属表面与细胞、组织的相容性。     

骨用镁合金表面Ti-Cu涂层的腐蚀行为

背景：镁合金作为骨折内固定材料具有力学性能与骨相近、生物相容性好和可降解等突出优点,但其在体液中降解速度过快,成为其临床应用的瓶颈,因此综合利用表面处理提高其耐蚀性能具有重要意义。 目的：综合运用磁控溅射技术和碱热处理技术在镁合金表面制备兼具耐蚀性能和生物活性的涂层。 方法：首先采用熔炼技术制备Mg-Zn-Mn合金,利用磁控溅射技术在材料表面制备致密涂层,然后利用碱性溶液对表面涂层进行处理,利用模拟体液浸泡实验研究涂层的腐蚀行为,通过表面产物中钙和磷的含量推测涂层的生物活性。 结果与结论：经磁控溅射和碱热处理技术在镁合金表面制备兼具耐蚀性能和生物活性的涂层;经模拟体液浸泡24和168 h后涂层表面沉积含Ca,P产物,Ca/P比分别为1.54和2.11,接近类骨磷酸盐Ca/P比,涂层表面的浸泡24 h形成5-10 μm点腐蚀,随着浸泡时间增加点腐蚀逐渐长大,浸泡168 h后点腐蚀增加为100-800 μm。     

阳极氧化伴水热处理制备纯钛羟基磷灰石薄涂层

为了解纯钛阳极氧化伴水热处理的技术路线及羟基磷灰石薄涂层在体内的成骨效应，以钛片为阳极，β－磷酸甘油钠和醋酸钙为电解质，经200－400V直流电解15min，维持电流密度≤50mA/cm^2，而后经280℃－300℃水热处理2h，取光滑，喷砂表面作对照，分别植入12只兔股骨内，枯术后4，8，16周取出带种植体骨块制作磨片，观察新骨生成情况及术后8周光滑和涂层种植体的界面超微结构，并作表面能谱分析，结果发现水热处理后，钛片表面出现了羟基磷灰石涂层，动物实验显示涂层种植体8周后编织骨的转化和成熟较快，未见剥脱的羟基磷灰石碎片，其表面的钙，磷含量在种植后增加明显，这说明阳极氧化伴水热处理可以制备出纯钛表面羟基磷灰石薄涂层，其早期促编织骨形成作用明显，可以加快编织骨转化成板层骨。     

Bone response to calcium phosphate-coated and bisphosphonate-immobilized titanium implants

Thin calcium phosphate (Ca-P) coatings have been introduced to overcome the shortcomings of plasma-sprayed Ca-P coatings. In our previous experiments, thin Ca-P coatings also enabled the immobilization of bisphosphonate, which is a drug used to treat osteoporosis. The present study was designed to evaluate the bone response to titanium implants treated with a thin Ca-P coating and bisphosphonate. Forty cylindrical commercially pure titanium implants with a length of 7 mm and a diameter of 3 mm were used as test implant fixtures. Three groups of surface-treated implants were prepared: (1) blasted with titanium powder and etched with a solution of 10% HF + 5% HNO3 (control); (2) modified with 0.5-microm thick Ca-P coatings and rapid heat-treating, and (3) immobilized with bisphosphonate by immersion in pamidronate disodium solution (10(-2) M) for 24 h at 37 degrees C. These surface-treated implants were inserted into edentulous areas in the mandibular molar region of five beagle dogs. After implantation periods of 4 and 12 weeks, the bone implant interface was evaluated histologically and histomorphometrically. All measurements were statistically evaluated using a one-way ANOVA and Fisher PLSD test for multiple comparisons among the means. Four weeks after the implantation, higher percentage of bone contact was found around the thin Ca-P-coated implants compared to that of the control group. The highest percentage of bone contact was found around the bisphosphonate-immobilized implants after 12 weeks of implantation. These data suggest that a thin coating of calcium phosphate followed by bisphosphonate-immobilization is effective in the promotion of osteogenesis on surfaces of dental implants.     

Radio frequency plasma treatments on titanium for enhancement of bioactivity

Titanium and its alloys, when treated in alkali solutions, are able to form calcium phosphate coatings on their surface after immersion in supersaturated solutions. In this study, the surfaces of titanium alloy discs were modified by an alkali treatment and a radio frequency (RF) plasma procedure (150 W and 13.56 MHz) in N(2), CO(2) or N(2)/O(2) (80/20%) atmospheres. After the alkali treatment, atomic force microscopy showed differences in the surface roughness of the samples. X-ray photoelectron microscopy indicated that the chemical composition of the surfaces changed after the different alkali and RF plasma treatments. The contact angles were also modified by approximately 5 degrees , making the original titanium surface more hydrophilic. Immersion in a supersaturated calcium phosphate solution was used to evaluate the bioactivity of the RF plasma-treated samples in vitro. Alkali-treated samples gave more homogeneous and thick coatings that those without alkali treatment. The use of RF plasma treatments enhanced the bioactivity of the samples, in particular for treatments performed in N(2) or N(2)/O(2) atmospheres. Energy-dispersive X-ray analysis indicated that coatings had Ca/P ratios between the values of octacalcium phosphate and hydroxyapatite. X-ray diffraction confirmed the presence of these two phases in most of the coatings. This study shows that an RF plasma treatment enhanced the bioactivity of titanium surfaces.     

The role of surface functional groups in calcium phosphate nucleation on titanium foil: a self-assembled monolayer technique

Surface functional groups play important roles in nucleating calcium phosphate deposition on surgical titanium implants. In this study, various functional groups were introduced onto the surface of commercially pure titanium foils using a self-assembled monolayer (SAM) technique. An organic silane, 7-oct-1-enyltrichlorosilane (OETS) was used and -OH, -PO4H2, -COOH groups were derived from its unsaturated double bond. Ti foils were first oxidized in concentrated H2SO4/H2O2. ESCA and contact angle measurements were used to characterize the SAM surfaces and confirm the presence of various functional groups. A fast calcium phosphate deposition experiment was carried out by mixing Ca2+- and (PO4)(3-)-containing solutions in the presence of the surface-modified Ti samples at pH 7.4 at room temperature in order to verify the nucleating abilities of these functional groups. SEM, Raman spectroscopy, XRD and ATR-FTIR results showed that poorly crystallized hydroxyapatite (HA) can be deposited on the SAM surfaces with -PO4H2 and -COOH functional groups, but not onto the SAM with -CH=CH2 and -OH. -PO4H2 exhibited a stronger nucleating ability than that of -COOH. The oxidized Ti sample also showed some calcium phosphate deposition but to a lesser extent as compared to SAM surfaces with -PO4H2 and -COOH. The pre-deposited HA can rapidly induce biomimetic apatite layer formation after immersion in 1.5 SBF for 18 h regardless of the amount of pre-deposited HA. The results suggested that the pre-deposition of HA onto these functionalized SAM surfaces might be an effective and fast way to prepare biomimetic apatite coatings on surgical implants.     

Incorporation of tobramycin into biomimetic hydroxyapatite coating on titanium

Calcium phosphate coatings containing an antibiotic were produced on titanium alloy (Ti6Al4V) implants using a biomimetic approach. Thin, amorphous calcium phosphate (ACP) coatings were first deposited onto Ti6Al4V plates by immersion in 5 times concentrated simulated body fluid (SBF), for 24h at 37 degrees C. The ACP-coated implants were then immersed in a supersaturated calcium phosphate (SCP) solution containing 0, 100, 200, 400, 600 or 800 mg/l of tobramycin for 48 h at 37 degrees C. A carbonated hydroxyapatite (CHA) layer, approximately 40 microm thick, was formed. Approximately 3 microg/mg of tobramycin was co-precipitated with the CHA crystals onto titanium alloy plates, using 800mg/l tobramycin in the coating solution. For comparison, plasma-sprayed calcium phosphate coatings were also immersed in solutions containing 100, 200, 400 or 1,000 mg/l of tobramycin for 10, 40 min, or 48 h. A maximum of about 0.3 microg/mg could be adsorbed onto the plasma-sprayed calcium phosphate coating with the comparable concentration of 800 mg/l in solution. The dissolution of coating and release of tobramycin were also measured in vitro using saline solution buffered at pH 5.0 or 7.3 at 37 degrees C. The release rate of tobramycin was faster at pH 7.3 than at pH 5, with 50 and 4 microg/ml/min, respectively. Tobramycin released from the biomimetic-coated plates could inhibit growth of Staphylococcus aureus bacteria. The result of this study, therefore, indicates that the biomimetic CHA coatings containing antibiotics could be used to prevent post-surgical infections in orthopaedic or trauma.     

Acid pretreatment of titanium implants

The purpose of this study was to evaluate the effectiveness of several methods of cleaning titanium surfaces as pretreatment for surface modifications by analyzing the chemical interaction of three acids, such as Na(2)S(2)O(8),H(2)SO(4) and HCl, followed by rinsing with acetone or ultrapure water. Chemical evaluation, using X-ray photoelectron spectroscopy (XPS), and mechanical evaluation, using nanoindentation, were employed. XPS revealed that an untreated Ti surface consisted of carbon- and nitrogen-containing contaminant and titanium oxide layer on metallic titanium substrate. The method involving the combination of 10 N HCl and acetone was the most effective of all the methods investigated. Such a combination most effectively reduced values of contamination parameters C/Ti and N/Ti, as well as the intensity of the titanium oxide component in Ti 2p spectra. Chlorine was barely detected from the surface treated with HCl in any concentration. Sulfur from the residual S(2)O(8)(2-) or SO(4)(2-), however, was detected from the samples treated with either Na(2)S(2)O(8) or H(2)SO(4). The S/Ti values depended on concentration of the acidic solution. In addition, nanoindentation measurements revealed that Young's modulus of the surface treated with 0.1-10 N HCl was not significantly different from that of an untreated surface (p > 0.05). Consequently, the HCl/acetone treatment is proposed as an excellent decontamination method for the surface preparation process of Ti.     

The removal torque of titanium screw inserted in rabbit tibia treated by dual acid etching

Chemical acid etching alone of the titanium implant surface have the potential to greatly enhance osseointegration without adding particulate matter (e.g. TPS or hydroxyapatite) or embedding surface contaminants (e.g. grit particles). The aims of the present study were to evaluate any differences between the machined and dual acid etching implants with the removal torque as well as topographic analysis. A total of 40 custom-made, screw-shaped, commercially pure titanium implants with length of 5 mm and an outer diameter of 3.75 mm were divided into 4 groups, 10 screws in each, and chemical modification of the titanium implant surfaces were achieved using HF and HCl/H(2)SO(4) dual acid etching. The first exposure was to hydrofluoric acid and the second was to a combination of hydrochloric acid and sulfuric acid. The tibia metaphysics was exposed by incisions through the skin, fascia, and periosteum. One implant of each group was inserted in every rabbit, 2 in each proximal tibia metaphysics. Every rabbit received 3 implants with acid etched surfaces and 1 implant with a machined surface. Twelve weeks post-surgically, 7 rabbits were sacrificed, Subsequently, the leg was stabilized and the implant was removed under reverse torque rotation with a digital torque gauge (Mark-10 Corporation, USA) (Fig. 1). Twelve weeks after implant placement, the removal torque mean values were the dual acid etched implants (24%HF+HCl/H(2)SO(4), group C) required a higher average force (34.7 Ncm), than the machined surface implants (group A) (p=0.045) (Mann-Whiteney test). Scanning electron micrographs of acid etching of the titanium surface created an even distribution of very small (1-2 microm) peaks and valleys, while machining of the titanium surface created typical microscopically grooved surface characteristics. Nonetheless, there was no difference in surface topography between each acid etched implant groups. Therefore, chemically acid etching implant surfaces have higher strengths of osseointegration than machined implant surfaces. There is less correlation between removal torque and the difference in HF volume%.     

Acid-induced bioactive titania surface

Nano- and conventional-TiO(2) powders were deposited onto titanium alloy using atmospheric plasma spraying technology. As-sprayed titania coatings were treated by H(2)SO(4) and HCl solutions at room temperature for 24 h, and the bioactivity was evaluated by simulated body fluid tests. Measured X-ray diffraction patterns indicated that as-sprayed titania coatings obtained from both nano and conventional powders were composed of primary rutile as well as a small quantity of anatase and Ti(3)O(5). The surface of as-sprayed coatings prepared from the conventional powder was rougher than that from nanopowder. After immersion in simulated body fluid for 2 weeks, both acid-treated nano- and titania coatings have induced carbonate-containing hydroxyapatite to form on the surfaces. However, this phenomenon did not appear on the surface of as-sprayed nano- and conventional-titania coatings. The results obtained indicated that the bioactivity of plasma sprayed titania coatings was improved by the acid treatment and had nothing to do with phase composition and particle size of the original TiO(2) powders.     

Hydrothermal crystallization of carbonate-containing hydroxyapatite coatings prepared by radiofrequency-magnetron sputtering method

Carbonate-containing hydroxyapatite (HA) films were prepared by low-temperature hydrothermal annealing from carbonate-containing calcium phosphate amorphous coatings on titanium substrates. The biocompatibility of the carbonate-containing HA layers was estimated by in vitro tests using simulated body fluid (SBF). Precursory amorphous coatings were deposited with rf-magnetron sputtering apparatus, using calcium phosphate glass target in Ar/CO2 atmosphere. The carbonate-containing HA coatings were successfully formed by the annealing at above 130 degrees C for 20 h. On the basis of SEM observation, about 2-microm thickness films coated rigidly were durable enough for the hydrothermal treatment. The coating layer was revealed to consist of single phase of PO4(-) and OH- partially carbonated HA by XRD and IR analyses. Overgrowing of bone-like apatite layers on the carbonate-containing HA surfaces in the SBF implied that the obtained films acquired a sufficient osteoconductivity, while it was still unclear that activity was enhanced, compared to pure HA coatings. The low-temperature hydrothermal annealing method was effective for preparation of rigid HA coatings on titanium as well as modification of their chemical compositions.     

Effect of substrate temperature on mechanical properties of calcium phosphate coatings

The effect of substrate temperature and processing parameters on mechanical properties of nanoscale calcium phosphate coatings are being studied in order to refine the processing technique for Functionally Graded Hydroxyapatite (FGHA) coatings. Coatings were deposited on titanium substrates with a set substrate temperature of 450, 550, 650, or 750 degrees C in an Ion Beam Assisted Deposition (IBAD) system using a sintered hydroxyapatite (HA) target. Mechanical properties of the coatings deposited with a set substrate temperature such as, bonding/adhesion strength to the substrate, nanohardness, and Young's Modulus as well as coating thickness were evaluated and compared with commercial plasma spray HA coatings. It is concluded that depositing FGHA coatings would better be started at 550-650 degrees C to maintain superior properties of the film at the interface. It can also be concluded that the residual stresses caused by different Coefficient of Thermal Expansions (CTEs) between the substrate and coatings are not the only factor controlling the bonding strength and mechanical properties of these samples. Other parameters such as the nature of the interface layers and their bonding to each other as well as the density and grain structure of the coatings must be taken into consideration for an appropriate evaluation of mechanical properties of calcium phosphate coatings deposited on heated substrate.     

Effect of the heating temperature on the corrosion resistance of alkali-treated titanium

The paper presents the results of examinations of the corrosion resistance of titanium after its being subjected to the surface modification by the alkali- and heat-treatments. The material examined was commercially pure titanium (grade 2). The samples were soaked in an aqueous 10M NaOH solution at 60 degrees C for 24 h and subsequently heated at 500, 600, or 700 degrees C for 1 h. The chemical composition of the surface layers was determined by X-ray photoelectron spectroscopy and secondary ion mass spectroscopy. The phases present in the layers were identified by XRD. The corrosion resistance was evaluated by electrochemical methods (Stern's method, potentiodynamic method, and impedance spectroscopy) at a temperature of 37 degrees C after short- and long-time exposures. The 13 h exposure was aimed to allow the corrosion potential to stabilize. The aim of the long-term exposures was to examine how the corrosion resistance of the modified samples changes during the exposure. Under the conditions prevailing during the experiments, the highest corrosion resistance was achieved with the samples heated at a temperature of 700 degrees C.