>The most questionable parts, again IMHO don't forget, are the W18 flap
>plates which are bonded into the wing ribs. These should be soft anodized
>for better fatigue resistance, kept chemically clean until bonded in, then
>the exposed part painted.
>
>If anyone has a better idea please explain.
>
>Graham
I would have added that anodising should be done at the last possible
moment. This reduces the negative effects of the slow hydration that takes
place to the oxide film and reduces the almost certain probability of
chemical contamination. The hydrated film has a much lower "surface free
energy", which is the opposite of what is required for a good bond (thats
the difference between clean diamonds and teflon, each at opposite ends of
the bond-strength spectrum).
And, to answer the original question about use of Alochrome (or similar),
I had very good results with this (removal of epoxy needs chiselling or
grinding and associated damage to metal), but can`t claim to have compared
it to electro-anodising. The chemical stuff has a limited shelf life and
needs to be fresh. I`ve found that heat-drying after alodising seems to
improve the strength of the bond; if bonded-in within minutes of treating.
Duncan McFadyean
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