Diagnosing the cause of dynamic compression plate premature failure
By Deen, K.M.; Farooq, A. & Sadiqui, N.A.
Published in Engineering Failure Analysis
2013
Abstract
The cause of premature failure of retrieved Dynamic Compression Plate (DCP) assembly from a 45 years old male was investigated by visual examination, chemical analysis of surface deposits by atomic absorption spectroscopy and Energy Dispersive spectroscopy coupled in a SEM. The electrochemical behavior of DCP and Screws was also evaluated in simulated body fluid through corrosion potential, Potentiodynamic Tafel scan and cyclic polarization. The chemical composition of DCP was not in conformity with ASTM F138-03. The higher concentration of 'Ni’ and 'Cr’ ions release and presence of chloride ions within the corrosion zone confirmed the dissolution of passive film by the aggressiveness of body environment. The negative corrosion potential, 2 times higher corrosion rate and varying passive current density of DCP than screws in simulated body fluid confirmed the higher susceptibility towards pitting and crevice corrosion. The higher protection tendency and breakdown potential with low passive current density of screws were also in support to lower corrosion tendency than DCP.