> Having just received the wing and fuselage kits for our XS
>Tri-gear, we have lots of steel and aluminium parts that would benefit from
>some corrosion protection before being assembled. We've been considering
>Alochrom 1200 for the alloy parts but does anybody know if an Alochrom
>surface is bondable? If not, what are the alternatives and what have other
>builders used on the steel components? I'm thinking mostly about the control
>runs fitted in the cockpit module which will be inaccessible after the
>cockpit module is fitted into the fus.
>Vanessa & Keith Summerhill. #450
Hard anodized and sealed will give the best protection. It doesn't stick
well to anything but should not need painting. It can be dyed.
For bonding, the anodizing should not be sealed but the fatigue life will
be compromised. IMHO, (humble opining), all parts should be designed to be
strong enough after anodizing.
I think I would hard anodize, seal, which is often boiling in hot water,
this fills the pores of the anodised coating. No, I don't know how. Natural
colour of decent alloys is a smart looking gray, so I would not bother
about painting. Paint hides the corrosion anyway.
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.
Steel components are usually cadmium plated. This is very hard to get done
in UK because of the heavy metal pollution prevention regime. I generally
go for zinc plating. Not quite as good but OK. In service a corrosion
resistant coating of LCF2 or Corrosion X or ACF 50 is not a bad thing. High
tech versions of the old Waxoil and very effective. All are available in
spray cans I think.
Assembly should always be done with chromate jointing compound, Duralac
here in UK. Helps to prevent intermetallic corrosion, if that's the right
term for it. Don't forget, carbon fibre will cause corrosion of steel parts
unless protected.
Graham
Graham
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