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Thread: Corrosion X in building a metal homebuilt.

  1. #11

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    All it takes is the onset of corrosion and it will propagate by itself. Trying to stop it can take much effort and expense, I'd opt for preventing it in the first place.

  2. #12
    rwanttaja's Avatar
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    Quote Originally Posted by martymayes View Post
    There are 60 yr old spam cans that have never seen a drop of primer, stored outside more than inside and they are still going strong.
    Then again, there was a run of Cessnas in the '70s where the company scrimped on the anti-corrosion prep; these have suffered a lot of corrosion.

    Case in point. Take a look at these three homebuilts:

    The blue single-engine one in the middle is the Wickham "A" ("Bluebird") that first flew in 1955, and the twin in the foreground is the Wickam "B", which flew about 1967. Both are all-metal, 2024, I believe. Though they might have been 7075. The third airplane is some obscure wooden type. :-)

    Anyway, the designer/builder of the first two was Jim Wickham, a configurator for Boeing Commercial Airplanes. It was his opinion that airplanes built from aluminum did not need additional corrosion protection, and neither of his airplanes were primed.

    The Bluebird (single-engine) was restored in the ~90s. Didn't hear of much anti-corrosion work needed. However, the Bluebird was an active airplane through most of its life, and was mostly hangared, I believe. The A&P who does my Condition Inspections did the restoration (and he parks the plane across the hangar row from my Fly Baby).

    The Model B (twin) was donated to a museum in ~1980, who parked it outside for 10-15 years until a chapter member bought it. He found massive corrosion in the wings.

    So....it's basically a crapshoot. If I were building something from 2024, *I* would prime the thing. And as Falcon21 says, if you apply Corrosion X during construction, don't expect to be able to paint the outside of the airplane. That stuff will weep through various holes (as it's designed to) and ruin any chance for paint adhesion on the outside.

    I like Bob's recommendation for Zinc Phosphate.

    Ron Wanttaja

  3. #13

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    One caution. Double check this but I have seen written that once a Corrosion-X is into a seam, paint will not longer stick. If that is true, primer is a better option. Corrosion-X after painting the exterior.

    Bust of luck,

    Wes

  4. #14

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    I would use Cor-Ban 35 . Boeing puts it on their planes and I used it at the airline I worked for . It is spray on or brush on and is a see thru rose colored texture . It dries and you can see thru it .. just a slight color . I think it is the best . Sky Geek sells it .

  5. #15

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    Cor-Ban video is on YouTube . Just put in "Cor-Ban" and the info will come up .

  6. #16
    Quote Originally Posted by martymayes View Post
    corrosion x has to be periodically reapplied to maintain it's effectiveness.

    I wouldn't use anything because aluminum has built in corrosion protection. Having the plane last 100 yrs would be about 80 yrs more than what I need at this point.
    This is the kind of bs info that the internet experts love to spread on forums. The only “built in” protection aluminum has is IF it is Alclad. If there is the tiniest scratch that alclad is compromised. Drill a hole and guess what, you’ve compromised the alclad. In reality the aluminum will out last you if untreated, but the big guys like Boeing prime everything. In critical areas they are assembled with wet primer. All external skins on pressurized aircraft have sealant applied. Built in protection indeed.

  7. #17

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    2024 corrodes very quickly with the least provocation. Aluminum is a very reactive metal.
    Drill a hole, put a screw in it, add liquid and wait. If the screw is stainless the aluminum will start to disappear. If the screw is cad plated, the plating will first corrode away; when it is gone, the aluminum will start to corrode. Google "Galvanic Corrosion".
    In Australia near the coast, they say; "you can hear the Cessnas Fizzing" as they corrode away.
    One turboprop I flew required a strip and inspection every three years due to corrosion issues; made of 2024.
    Corrosion proof your project! You will not be sorry.

  8. #18

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    Quote Originally Posted by Paulie123 View Post
    In reality the aluminum will out last you if untreated,
    Yes, that's what I said. No need to take it out of context.

  9. #19

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    Quote Originally Posted by la4 View Post
    In Australia near the coast, they say; "you can hear the Cessnas Fizzing" as they corrode away.
    Geography makes a difference. When I lived on the Gulf Coast, a helicopter operator had it down to a science. They knew exactly how often a refub was needed and they knew when they put a helo in service how many yrs it would last. ACF-50 treatments were a routine maintenance item.
    On the other hand, 20+ y/o fish spotters flying Cessna 172's over the same water would rack up 20,0000 hrs with the standard Cessna corrosion package - nothing but paint - which was sparse after 20 yrs of abuse. They did get a routine ACF-50 bath as well.
    Where I live now, as long as you don't drive your plane down the highway in the winter, not much salt exposure.

  10. #20

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    Quote Originally Posted by rwanttaja View Post
    Then again, there was a run of Cessnas in the '70s where the company scrimped on the anti-corrosion prep; these have suffered a lot of corrosion.
    Ron, wasn't the Cessna filiform corrosion in the '70's partly caused by Cessna during their switch to modified polyurethane finishes?

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