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View Diary: Maritime Hoovervilles in Portland, Oregon (103 comments)

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  •  This is fresh water, but in Puget Sound, you'd (5+ / 0-)

    have that problem.

    You have exactly 10 seconds to change that look of disgusting pity into one of enormous respect!

    by Cartoon Peril on Sun Oct 21, 2012 at 09:05:43 AM PDT

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    •  It can be an issue in fresh water and estuaries (7+ / 0-)

      It's a whole lot slower in fresh water unless you're parked next to someone with a stray current problem on their boat.

      One thing about corrosion in general...zinc anodes are inactive in fresh water.  Magnesium is the traditional solution, but aluminum is better.

      "First they ignore you, then they laugh at you, then they fight you, then you win". Mohandas K. Gandhi

      by DaveinBremerton on Sun Oct 21, 2012 at 09:25:34 AM PDT

      [ Parent ]

      •  There are probably about 10 or so... (6+ / 0-)

        live aboards floating in Bellingham Bay, along the lee shore of the east side of the bay. There are about another 20 or so that appear to be just moored, not occupied. Not all that great an anchorage when a storm with winds from the west or north blows in, but most of the time it is reasonably calm(er) water.

        It's my hometown, and although I'm not there now, over the last few years from my parents house you could see the numbers of boats moored out increase slowly over time. There were just a few at first, and my thinking was it was because the marina fees got to be too much, but it is now obvious they are folk without much else. A couple are nice small, oceanic sailing yachts, but most are old fiberglass or wood yachts, just like Portland.

        I would not want to be on the river in winter, especially during one of Portland's wonderful ice storms...

      •  Zinc is inactive in fresh water? Really? (1+ / 0-)
        Recommended by:
        DaveinBremerton

        Really? How do you apply magnesium?
        Right now the all purpose protective material of choice is a two part epoxy coating called Interprotect.

        •  I think we're talking two different issues (2+ / 0-)
          Recommended by:
          bluedust, Cartoon Peril

          Epoxy coatings are great for protecting aluminum hulls.  As with any paint on an aluminum hull, the first layer must be a copper-free barrier paint.

          When I say "underwater metal" I'm referring to thru-hulls, props, drive shafts, rudders, outdrives, etc.  Since these are not normally painted, there is (or should be) a sacrificial anode to protect them.  Most of the time, the anode is protecting a large mass of aluminum (outdrives, outboard lower units, etc) from the other underwater metal (props, shafts, and thru-hulls of bronze, stainless, nibral, aquamet, or a host of other items that don't play nice with aluminum).

          Zinc does a great job of protecting aluminum in salt water.  However, in brackish or fresh water the zinc doesn't generate enough of a DC voltage shift to protect aluminum.  A zinc anode will tend to develop a calcite crust--if your zinc anode seems to last forever and is covered with a white film, you might want to get your hull potential checked.

          Corrosion is a weird world.  I recently worked an issue where a stainless thru-hull was corroding within a few days of being placed in salt water.  The problem turned out to be the thru-hull was custom-machined and the machine shop didn't passivate the thru-hull afterwards.  That left a layer of carbon steel on the surface of what was otherwise good 316 stainless.

          "First they ignore you, then they laugh at you, then they fight you, then you win". Mohandas K. Gandhi

          by DaveinBremerton on Sun Oct 21, 2012 at 09:06:43 PM PDT

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