Preventing corrosion on 80% lower

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  • AngusNGuns

    Member
    Nov 27, 2019
    6
    Those of you that have built 80% ar lowers... I’m talking you bought one with at was already anodized.... how have you prevented corrosion in the freshly milled portions of the receiver? I’m looking at some flat dark earth receivers but I’m not sure how to protect the raw aluminum if anything at all? Thought about just masking everything off and spraying some high temp engine paint?

    Also, those of you that used a raw aluminum lower..... would it be easier to just buy a raw lower then cerakote the whole thing flat dark earth?
     

    GuitarmanNick

    Ultimate Member
    Jan 9, 2017
    2,221
    Laurel
    Mine were all anodized, are not coated after milling, and show no signs of corrosion so far.

    I would suggest that you to consider the thickness of any coating and allow for it in the milling process to insure the internal parts have sufficient space to operate without restriction.
     

    foodpoison

    Ultimate Member
    MDS Supporter
    Jan 19, 2013
    2,165
    the Dena
    aluminum forms an oxidized layer on the surface almost immediately when milled, cut ,or scratched. this prevents corrosion on raw aluminum
     

    letmeoutpax

    Active Member
    Nov 12, 2013
    474
    St. Mary's
    If you keep it clean and dry aluminum is pretty stable. Most climbing carabiners are bare aluminum and as long as your inspection does not find a crack you can assume they are still full strength. Salt water is the most common thing you want to avoid. You could spray some primer inside the machined pocket for peace of mind.
     

    randomuser

    Ultimate Member
    Nov 12, 2018
    5,775
    Baltimore County
    My last sailboat was 1978. It was kept in the water the entirety of its life. The mast was aluminum. The air was salty. No corrosion or pitting that I had on the mast would have affected the functionality of a lower. I sold the boat in 2018. Do the math on the exposure time of that aluminum and don't worry about your lower. Good job on making an 80%. I love seeing people build them.


    The "discoloration" you might see on your lower is simply oxidation that actually protects the metal.
     

    Decoy

    Ultimate Member
    MDS Supporter
    Mar 2, 2007
    4,926
    Dystopia
    I have machined raw aluminum parts that have been outside for over 10 years and they have no signs of wear other than being discolored. I would just leave it, but if you are really concerned I know some people use Brownells ALUMA-HYDE.
     

    Pinecone

    Ultimate Member
    MDS Supporter
    Feb 4, 2013
    28,175
    Yes, pure aluminum creates its own coating to prevent corrosive, that is not true of many of the aluminum alloys.

    The sheet aluminum using in aircraft is usually ALCLAD. Which is alloy sheet, with a thin pure aluminum on each face.

    You can use any number of pain type coatings to prevent any possible corrosion. Or just keep a coating of grease or oil on it.
     

    Dave.B

    Ultimate Member
    MDS Supporter
    May 15, 2011
    2,885
    If you are really that concerned about it you can pick up an Alodine 1132 pen. They're not cheap though. The plus side is you don't have to rinse the area in D water after coating
     

    fidelity

    piled higher and deeper
    MDS Supporter
    Aug 15, 2012
    22,400
    Frederick County
    Just a related FYI in discussing potential aluminum corrosion, aluminum can be susceptible to galvanic corrosion if in direct contact with steel. In SOTAR AR-15 maintenance and build classes, AeroShell grease was used at contact points between these metals.
     

    Dave.B

    Ultimate Member
    MDS Supporter
    May 15, 2011
    2,885
    Just a related FYI in discussing potential aluminum corrosion, aluminum can be susceptible to galvanic corrosion if in direct contact with steel. In SOTAR AR-15 maintenance and build classes, AeroShell grease was used at contact points between these metals.

    you would need an electrolyte present for galvanic corrosion to occur between dissimilar metals. If the anodize coating is in place and the mating surface has not been galled exposing raw aluminum I wouldn't worry about it. The grease wouldn't hurt though for lubrication of moving parts.
     

    jrumann59

    DILLIGAF
    MDS Supporter
    Feb 17, 2011
    14,024
    you would need an electrolyte present for galvanic corrosion to occur between dissimilar metals. If the anodize coating is in place and the mating surface has not been galled exposing raw aluminum I wouldn't worry about it. The grease wouldn't hurt though for lubrication of moving parts.

    firing and handling a gun introduces elctrolytes into the environment. Maybe sweat maybe by products from burnt and unburnt gunpowder.
     

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