Aluminum Corrosion in hull floor in Engine Room

Discussion in 'Materials' started by mydauphin, Apr 24, 2018.

  1. mydauphin
    Joined: Apr 2007
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    Location: Florida

    mydauphin Senior Member

    After cleaning my blige I found a couple of blisters on the aluminum hull floor under engines. When I removed the blister about half of the depth of the aluminum plate is gone in the area about 1 inch by 2 inches. Structurally I am not worried about it but want to stop this corrosion and possibly repair it. Problem is Aluminum boat is in the water and its kind of large to take out. I am thinking I might be able to low temp braze/solder some zinc or aluminum/zinc alloy into the hole even though I won't be able to bring hull up to welding temperature. Another thought would be some kind of zinc chromate and then some epoxy, but I am afraid corrosion would continue around it.
     
  2. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Before you do anything, you need to establish the cause of the corrosion.
     
  3. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    I think it is a good idea to have sacrificial anodes in the bilges.
     
  4. Ad Hoc
    Joined: Oct 2008
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    Location: Japan

    Ad Hoc Naval Architect

    We always paint the bilges of our hulls with white/grey epoxy paint.
    Shows up dirt/grease and prevents the basic forms of corrosion starting too...
     
  5. mydauphin
    Joined: Apr 2007
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    Location: Florida

    mydauphin Senior Member

    I have all my bilges painted and treated except this one. I think what happened is some rust from something on the engine fell there and was covered up by oil.
     

  6. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    A low temperature braze will handle the pitting or divot, but John is correct, find out what caused it. My recommendation is have a plastic drip pan made or make one yourself. A catch pan can solve a number of problems and make life easier in your bilge. Yeah, it's an area that absolutely sucks to work in, but a lot of stuff can be unbolted a swung to the side. The last one I made I used 1" foam, glued together in pieces for removal, shaped to custom fit the area. It had rolled lips, a drain sump and flange for a fitting, ribs to stand it off the bilge, etc. Once the pieces were removed, I used them as a male mold to layup some bias and mat. The fitting was tapped, edges smoothed and I was able to slide it back in place as a two piece assembly, which was bonded together with some goo and tape. I can now change oil by letting it run into the pan and draining it off afterward, though I haven't done this, I could in a pinch.
     
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