Mechanisms responsible for synergy between fretting and corrosion for three biomaterials in saline solution

The material removal caused by synergistic interaction of fretting and corr osion is much larger than the summation of individual fretting and corrosio n loss. The increment of removal should result from the synergistic effect of mechanical and corrosive losses of materials, i.e. the acceleration of c orrosion by fretting and the increase of fretting by corrosion. The frettin g corrosion behaviors of three biomaterials, 316L stainless steel, Co-Cr-Mo and Ti-6Al-4V alloys were investigated. The total removals of materials sh ould come from five components, pure corrosion, pure wear, corrosion increm ent caused by fretting, fretting increment caused by corrosion and synergy. Experimental results showed that the dissolution processes of three materi als were accelerated significantly by fretting. The approximate removals of materials caused by synergy in saline solution are 31.6% for 316L stainles s steel, 15.3% for Co-Cr-Mo alloy and 7.2% for Ti-6Al-4V alloy of total los s, respectively. The corrosion alone was a small percentage, just accountin g for about 3% of total loss for three materials. The synergistic process o f three materials was discussed based on three important stages, pure frett ing, pure corrosion and synergy. The results suggested that both factors of materials and surface contact state should be considered simultaneously fo r the protection of three biomaterials under fretting corrosion conditions. The possible mechanism responsible for synergy between fretting and corros ion was also discussed. (C) 2001 Elsevier Science B.V. All rights reserved.