hard anodising

huangyhg

hard anodising
i have a 7075 thread that has been hard anodised instead of sulphuric anodised and i have to determine the effect on fatigue life. anyone know where i can get data on comparable fatigue life after hard anodising?
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here are some threads from this site.  also, have you checked mil std 8625 for any data on this subject
you might assume the existence of the minimum depth crack you can't find under dye-penetrant inspection.  then calculate crack propagation using nasa flagro or the current equivalent.  
with hard-anodizing and the stress-concentration of a thread form (see peterson), i would expect cracking immediatly upon preloading.  
the sulphuric acid process itself does not guarantee an improvement; it's the boiling-water sealing step that forms a relatively amorphous emulsion which should be more crack-resistant.
?why anodizing? there are many other more historical protective processes, including mil 5541 (alodine) and wet installation with epoxy primer.  
i've never seen any actual data on any of the above.