I have always used Alodine (a sort of DIY anodising) and epoxy chromate primer
on my alloy bits. Believe me, if you want to remove the stuff you will have to
grind it off!
Alodine is not supposed to be quite as good as factory anodising but does score
in two significant areas. These are:
1. The bond of the primer is crucially affected by contamination of the
treated surface (one finger print is enough contamination). With Alodine, the
treated surface can be painted within minutes of treatment, thus minimising the
opportunity for comtamination. Unless parts returned from the anodisers are
thoroughly redegreased, there is a good chance that bond strength will be
adversely affected.
2. Anodised surfaces will slowly hydrate which reduces the strength of
the subsequently applied bond . Boeing have developed a proprietry technique
(involving the use of phosphoric acid) which inhibits this and allows longer
storage of parts before use.
As our noble leader says, "cleanliness is next to Godliness".
All IMHO of course.
Rgds Duncan McFadyean
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