Analysis of failed bolt-type power connectors showed seriouscontamination and low contact force (Luo et al, 1999). Further studiesshow that combined fretting and corrosion effects greatly aggravateconnection performance. Electrochemical corrosion occurs and whitecorrosion products are observed between Al connector and steel flatwasher. XPS shows that the product is mainly a compound ofAl2O3 and its hydrate. Crevice corrosion betweennut, lock washer and flat washer is also found. Corrosion not onlydecreases mechanical strength, but also reduces the lock washerload-bearing area. Several lock washers and connectors have cracks attheir maximum tension stress position, which is evidence of stresscorrosion. This corrosion damage may develop soon after a period oflatency, quickly causes loss of contact force, and is much moredangerous than other kinds of corrosion. Reduced compressive forceallows fretting to take place at contact interfaces. Analysis showsvarious kinds of micro-motion at contact interfaces, with one-third ofsamples showing fretting tracks. A tarnish film of oxide debris and dustaccumulates on the contact surface. Connection resistance increases,body temperature increases and corrosion is thus accelerated. This cyclemay finally cause connector failure. Therefore, appropriate protectivemeasures are needed for harsh environments. Surface analysis devicessuch as SEM/EDS and XPS are used to observe electric contact interfacemorphology and analyze corrosion product compound formation.Metallographic examination is also used to analyze corrosion productsand metallurgical structure
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