ASTM F1875 Corrosion test of taper connections
This practice describes the testing, analytical, and characterization methods for evaluating the mechanical stability of the taper connection of modular hip implants subjected to cyclic loading by measurements of fretting corrosion. Two test methods described are as follows:
The taper connection is placed in a test chamber with an electrolyte solution (0.9% NaCl) and loaded over 10 million cycles in accordance with ASTM F 1140. The isolated fluid is chemically tested for particles and ions. The components of the taper connection are then examined microscopically and electron microscopically. In addition, weight loss can serve as a measurement of abrasion. The method quantitatively measures the particles and ions and qualitatively the destruction of the taper surface by micro motion and corrosion.
This method provides for short-term electrochemical evaluation of the fretting corrosion of the modular interface. It is not the intent of this method to produce damage nor particulate debris but rather to provide a rapid method for qualitative assessment of design changes which do not include material changes.
The endoprosthesis is positioned in a test chamber with an electrolyte solution (0.9% NaCl). The chamber is filled so far that the electrolyte covers the taper connection and a part of the stem. The contact surfaces are isolated from the electrolyte. The taper connection is loaded as per method 1 according to ASTM F 1140, whereby the forces and test frequency can be lower.
- Procedure B:
A large surface counterelectrode is positioned in the solution to simulate the stem surface. An amperemeter is connected between the endoprosthesis and the counterelectrode. The difference before and during the load is a measure of the abrasion corrosion between the cone and the head of the hip endoprosthesis.
- Procedure A:
A calomel electrode serves as a reference for the measurement of the corrosion potential with the voltmeter. The test is terminated when a potential is established.