Significance and Use
3.1 Implantable medical devices can be made of dissimilar metals or come into electrical contact with dissimilar metals leading to the potential for galvanic corrosion, which may result in the release of corrosion products with harmful biological consequences or a compromise of structural integrity of the device. Therefore, it is important to determine the susceptibility of these types of devices to galvanic corrosion.
3.2 Use of this test method is intended to provide information on the possible galvanic component of corrosion of two dissimilar metals in contact with one another. The dissimilar metals in contact may be on the same implantable medical device or as component parts of individual medical implant devices.
3.3 This test method has been designed to accommodate a wide variety of device shapes and sizes encountered by allowing the use of a variety of holding devices.
3.4 This standard is presented as a test method for conducting galvanic corrosion tests in a simulated physiological environment. Adherence to this test method should aid in avoiding some of the inherent difficulties in such testing. Other standards such as Guide G71 are general and, while they provide valuable background information, do not provide the necessary details or specificity for testing medical device implants.
Scope
1.1 This test method covers conducting galvanic corrosion tests to characterize the behavior of two dissimilar metals in electrical contact that are to be used in the human body as medical implants or as component parts to medical implants. Examples of the types of devices that might be assessed include overlapping stents of different alloys, stent and stent marker combinations, orthopedic plates and screws where one or more of the screws are of a different alloy than the rest of the device, and multi-part constructs where two or more alloys are used for the various component parts. Devices which are to be partially implanted, but in long-term contact within the body (such as external fixation devices) may also be evaluated using this 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 the behavior of galvanic couples in an electrolyte.
1.3 Devices and device components are intended to be tested in their finished condition, as would be implanted (that is, the metallurgical and surface condition of the sample should be in or as close as possible to the same condition as in the finished device).
1.4 This test method does not address other types of corrosion and degradation damage that may occur in a device such as fretting, crevices, or the effect of any galvanically induced potentials on stress corrosion and corrosion fatigue. Surface modifications, such as from scratches (possibly introduced during implantation) or effects of welding (during manufacture), are also not addressed. These mechanisms are outside of the scope of this test method.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 Warning—Mercury has been designated by many regulatory agencies as a hazardous substance that can cause serious medical issues. Mercury, or its vapor, has been demonstrated to be hazardous to health and corrosive to materials. Use caution when handling mercury and mercury-containing products. See the applicable product Safety Data Sheet (SDS) for additional information. The potential exists that selling mercury or mercury-containing products, or both, is prohibited by local or national law. Users must determine legality of sales in their location.
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
NOTE 1: Additional information on galvanic corrosion testing and examples of the conduct and evaluation of galvanic corrosion tests in electrolytes are given.2
1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
