1、Designation: F3044 14Test Method forStandard Test Method for Evaluating the Potential forGalvanic Corrosion for Medical Implants1This standard is issued under the fixed designation F3044; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revis
2、ion, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers conducting galvanic corrosiontests to characterize the behavior of two dissim
3、ilar metals inelectrical contact that are to be used in the human body asmedical implants or as component parts to medical implants.Examples of the types of devices that might be assessedinclude overlapping stents of different alloys, stent and stentmarker combinations, orthopedic plates and screws
4、where oneor more of the screws are of a different alloy than the rest of thedevice, and multi-part constructs where two or more alloys areused for the various component parts. Devices which are to bepartially implanted, but in long-term contact within the body(such as external fixation devices) may
5、also be evaluated usingthis method.1.2 This test method covers the selection of specimens,specimen preparation, test environment, method of exposure,and method for evaluating the results to characterize thebehavior of galvanic couples in an electrolyte.1.3 Devices and device components are intended
6、to betested in their finished condition, as would be implanted (thatis, the metallurgical and surface condition of the sample shouldbe in or as close as possible to the same condition as in thefinished device).1.4 This test method does not address other types ofcorrosion and degradation damage that
7、may occur in a devicesuch as fretting, crevices, or the effect of any galvanicallyinduced potentials on stress corrosion and corrosion fatigue.Surface modifications, such as from scratches (possibly intro-duced during implantation) or effects of welding (duringmanufacture), are also not addressed. T
8、hese mechanisms areoutside of the scope of this test method.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-b
9、ility of regulatory limitations prior to use.NOTE 1Additional information on galvanic corrosion testing andexamples of the conduct and evaluation of galvanic corrosion tests inelectrolytes are given in Ref. (1).22. Referenced Documents2.1 ASTM Standards:3D1193 Specification for Reagent WaterF2129 Te
10、st Method for Conducting Cyclic PotentiodynamicPolarization Measurements to Determine the CorrosionSusceptibility of Small Implant DevicesG1 Practice for Preparing, Cleaning, and Evaluating Corro-sion Test SpecimensG3 Practice for Conventions Applicable to ElectrochemicalMeasurements in Corrosion Te
11、stingG5 Reference Test Method for Making PotentiodynamicAnodic Polarization MeasurementsG15 Terminology Relating to Corrosion and Corrosion Test-ing (Withdrawn 2010)4G16 Guide for Applying Statistics to Analysis of CorrosionDataG31 Guide for Laboratory Immersion Corrosion Testing ofMetalsG46 Guide f
12、or Examination and Evaluation of Pitting Cor-rosionG59 Test Method for Conducting Potentiodynamic Polariza-tion Resistance MeasurementsG71 Guide for Conducting and Evaluating Galvanic Corro-sion Tests in ElectrolytesG82 Guide for Development and Use of a Galvanic Seriesfor Predicting Galvanic Corros
13、ion PerformanceG102 Practice for Calculation of Corrosion Rates and Re-lated Information from Electrochemical Measurements3. Significance and Use3.1 Implantable medical devices can be made of dissimilarmetals or come into electrical contact with dissimilar metals1This test method is under the jurisd
14、iction of ASTM Committee F04 on Medicaland Surgical Materials and Devices and is the direct responsibility of SubcommitteeF04.15 on Material Test Methods.Current edition approved Jan. 15, 2014. Published May 2014. DOI: 10.1520/F3044-14.2The boldface number in parentheses refers to the reference prov
15、ided at the endof the document.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4The last approved version of
16、this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1leading to the potential for galvanic corrosion, which mayresult in the release of corrosion products with harmfulbiological consequ
17、ences or a compromise of structural integ-rity of the device. Therefore, it is important to determine thesusceptibility of these types of devices to galvanic corrosion.3.2 Use of this test method is intended to provide informa-tion on the possible galvanic component of corrosion of twodissimilar met
18、als in contact with one another. The dissimilarmetals in contact may be on the same implantable medicaldevice or as component parts of individual medical implantdevices.3.3 This test method has been designed to accommodate awide variety of device shapes and sizes encountered byallowing the use of a
19、variety of holding devices.3.4 This standard is presented as a test method for conduct-ing galvanic corrosion tests in a simulated physiologicalenvironment. Adherence to this test method should aid inavoiding some of the inherent difficulties in such testing. Otherstandards such as Guide G71 are gen
20、eral and, while theyprovide valuable background information, do not provide thenecessary details or specificity for testing medical deviceimplants.4. Apparatus4.1 Potentiostat, verified in accordance with Reference TestMethod G5. Other means of verifying the accuracy andreliability of the potentiost
21、at may be used, so long as this isadequately documented. For this test method, the potentiostatshould be a high impedance instrument configured as a zeroresistance ammeter (ZRA). Alternatively, a setup consisting ofa dedicated ZRA, an electrometer and a two-channel recorderfor recording the galvanic
22、 current and galvanic potential withtime can be used. The currents measured during the test arelikely in the nA range (or lower). The instrument used shouldbe capable of reliably measuring such currents.4.2 The Tested Samples, prepared as individual electrodes ofthe galvanic couple. The configuratio
23、n of each electrode andholder will depend on the type of specimen being tested, asdescribed in 5.2. The sample holder can be of variousconfigurations, provided it allows for good electrical connec-tion to the sample, provides a method of electrical connectionoutside of the test cell, ensures that th
24、e sample sits fully belowthe liquid level line in the test cell, does not come into physicalcontact with any other element of the cell or apparatus, andallows for masking of the sample at the point of connection.4.3 Reference Electrodea verified saturated calomel elec-trode (SCE), as described in Re
25、ference Test Method G5,isthepreferred reference electrode. If another standard electrode isused (for example, Ag/AgCl), data should be adjusted so that itis reported with respect to SCE.4.4 Salt Bridge, such as a Luggin probe, may be usedbetween the working and reference electrode, such as the types
26、hown in Reference Test Method G5.4.5 Suitable Polarization Cell, with a volume of at least 500cm3, equivalent to or similar to that recommended in ReferenceTest Method G5. The volume of the cell may be greater than500 cm3if needed to accommodate a larger sample.4.6 Water Bath, or other heating appli
27、ance capable ofmaintaining the test solution temperature at 37 6 1C. Notethat use of a hot plate to heat and/or agitate the solution (forexample, using a magnetic stir bar) can cause excessive noiseand interfere with the electrochemical data.4.7 Gas Bubbler, to provide aeration and agitation, capabl
28、eof delivering aeration at a rate of 150 cm3/min.4.8 Thermometer, with an accuracy for measurement within61C.4.9 pH meter, with an accuracy for measurement within60.1.4.10 An example of a typical test cell set-up is provided inFig. X2.1.5. Test Specimens5.1 MaterialUnless otherwise justified, all sa
29、mples se-lected for testing should be taken from finished product that hasbeen subjected to all normal manufacturing processes and isconsidered acceptable for clinical use. Cosmetic rejects orother nonclinical samples may be used if the cause for rejectionwould not affect the galvanic corrosion beha
30、vior of the device,but the metallurgical and surface condition of the sampleshould be in or as close as possible to the same condition as thefinished device. Sterilization or other manufacturing processesmay be omitted if it can be demonstrated that these processeshave no effect on the galvanic corr
31、osion behavior of the device.NOTE 2Loading or deployment of samples, as it would occur in vivo,should be simulated as closely as is reasonably possible, since theseactions can potentially affect the overall corrosion behavior of thematerial. Because anode and cathode must be separated for testing, i
32、t isunderstood that this step may not be possible.5.2 Selection of Anode and Cathode:5.2.1 It is preferable to evaluate the components before thetest is initiated to determine which one would likely be theanode and which would be the cathode. For example, in adevice containing two alloys, such as a
33、stent with markers, onematerial will be the anode and the other will be the cathode.5.2.2 Published galvanic series are available to help with thedetermination of anode/cathode (see Guide G82, for instance.)However, it should be remembered that these series arepublished for specific electrolytes, wh
34、ich may or may notaccurately represent the test electrolyte or in vivo conditions.Alternatively, the open circuit potential (OCP) can be mea-sured for each material in the chosen electrolyte, in order toestablish their relative positions electrochemically. The mate-rial with the less noble value of
35、the OCP will likely be theanode.NOTE 3Open circuit potential, for the purpose of determining anodicor cathodic condition, should be measured after a minimum of1hincontact with the solution. The samples used for this measurement shouldnot then be used in the galvanic test.5.2.3 Where a choice exists
36、as to the relative sizes of theanode and cathode (for example, if the device comes in severalsizes and the anode-to-cathode surface area ratio is different forF3044 142different sizes), it should be remembered that the most aggres-sive galvanic couple occurs with a smaller anode relative to alarger
37、cathode.5.2.4 In the case where three or more alloys are to be testedfor their galvanic corrosion behavior, the single most activecomponent (anode) should be tested against a combination ofthe other components. If more than one component of amulti-component device is suspected of being prone to gal-
38、vanic corrosion, each can be tested against the rest of thecomponents joined together. Joining requires mounting com-ponents together in electrical contact with one another, as asingle electrode (or electrode bundle). This may be accom-plished by joining the electrical connections to the componentso
39、utside the cell or by joining components that are to be exposedtogether inside the cell. The latter may require spot welding orother techniques. It is important to mask off any areas that arespot welded or otherwise altered from their original formduring connection and mounting, so that these areas
40、do notbecome part of the test. Materials suitable for use in maskingshould be impermeable to water and capable of isolating thearea masked off, without contributing unwanted crevice effects.5.2.5 The anode and cathode should be separated for testing.In some devices, particularly those containing com
41、plex, multi-alloy component parts that may be fused or brazed together,separation of anode and cathode may be difficult or impossible.In these cases, it is acceptable to mask off various areas of thepart, leaving only the desired material(s) exposed.5.2.6 Where possible, as much of the device as pos
42、sibleshould be tested while maintaining the ratio of surface areasbetween anode and cathode. It is understood that small area(s)of the device will likely be masked off due to fixturingrequirements.5.3 Surface Area Calculation:5.3.1 The relative surface area ratio of anode material tocathode material
43、 in the test samples should be maintained (thatis, mimic the actual device) during the test. A worst case ratiomay be used, but this should be based on a ratio that canactually occur in the device based on device tolerances, sizevariations, or differences in intended usage (see 5.2.3). Anartificial
44、worst case (for example, choosing a ratio that does notoccur or is artificially high), is not recommended.5.3.2 The surface area of the entire anode and entire cathodeshould be calculated from drawings or measurements. The areawhere the material is connected to the testing apparatus, whichis masked,
45、 should be subtracted. In the case of stents contain-ing multiple markers, the total exposed surface area of themarkers should be used.5.3.2.1 Ideally, decoupling the anode and cathode can beaccomplished such that entire sub-component parts may betested. In this case, the surface area ratio of anode
46、 to cathodeshould naturally be preserved. In some cases, however, it maynot be practicable to decouple the materials of interest whilepreserving the components. In these cases, a test specimen maybe used to simulate the total area of the material of interest. Forexample, if a stent with multiple mar
47、kers is to be tested, asingle piece of the marker material (such as a strip, tube, orsheet that is in as close as possible to the same metallurgicalcondition as the markers themselves) with area equal to thetotal surface area of the exposed marker material in the devicemay be tested against a single
48、 bare stent with markers removedor masked.5.4 Number of Specimens: As a minimum, duplicate andpreferably triplicate specimens should be tested to determinethe variability in the galvanic corrosion behavior. The effect ofthe number of replications on the application of the results isset forth in Guid
49、e G16.6. Test Environment6.1 The test solution should be chosen to approximate theintended in vivo environment.6.2 Reagent grade chemicals should be used for this testmethod. Such reagents should conform to the specifications ofthe Committee onAnalytical Reagents of theAmerican Chemi-cal Society.56.3 The water should be distilled or deionized (DI) andshould conform to the purity requirements of SpecificationD1193, Type IV reagent water.6.4 Unless otherwise specified, phosphate buffered saline(PBS) should be used as the standard test solution. A variety ofsimulated physiological
