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I'm not trying to stir the pot but was reading an interesting article about this in "Marine Systems Excelence Emagazine"
and thought I'd pass along this excerpt:
Suitable Alloys
The requirement for corrosion resistance limits the range of materials from which seacocks and their related components may be made. Only bronze, DZR (more on that in a moment) brass, glass-reinforced plastic and, in some cases, stainless steel may be used. The terms “brass” and “bronze” encompass a wide range of copper alloys. The primary determining factor is zinc content. Zinc is an especially ignoble metal; it corrodes very easily when in the presence of other metals and an electrolyte, such as seawater, which is why it’s used in sacrificial anodes. Zinc, however, also imparts strength to copper, mixing the two, often in about a 40-60 ratio respectively, results in a brass suitable for clocks, lamps and cabin hardware, but most definitely not, with few exceptions, for seawater plumbing.
Copper-zinc alloys used below the waterline undergo a process called dezincification whereby the zinc corrodes from the alloy, leaving behind a pink, porous and very fragile structure that’s almost certain to fail. For the most part, true bronze alloys are zinc-free, their primary elements being copper and tin. Other alloying elements include silicon and nickel (technically making them something other than bronze, but still acceptable for use in seawater plumbing). These are the best alloys for use below the waterline because they are not susceptible to dezincification
Unfortunately, a huge range of alloys lies between true bronze with no, or very little zinc and true brass which contains a high percentage of zinc. Two common alloys often used in marine applications are 85-5-5-5 (or C83600) and DZR.
85-5-5-5 contains 85 percent copper, 5 percent zinc, 5 percent lead and 5 percent silicon and can be used below the waterline.
Some European manufacturers use something referred to as DZR brass, a dezincification-resistant brass alloy. This alloy has a higher zinc composition than many other copper alloys (30 percent or more), but it also includes trace amounts of other metals meant to retard zinc corrosion or leaching.
Neither of these alloys resists dezincification nearly as well as the zinc-free or near-zinc free bronze alternatives; but as they are less expensive and unlikely to become a problem in the early years of the boat’s life, they can be an attractive alternative for more cost conscious builder.
I'm not trying to stir the pot but was reading an interesting article about this in "Marine Systems Excelence Emagazine"
and thought I'd pass along this excerpt:
Suitable Alloys
The requirement for corrosion resistance limits the range of materials from which seacocks and their related components may be made. Only bronze, DZR (more on that in a moment) brass, glass-reinforced plastic and, in some cases, stainless steel may be used. The terms “brass” and “bronze” encompass a wide range of copper alloys. The primary determining factor is zinc content. Zinc is an especially ignoble metal; it corrodes very easily when in the presence of other metals and an electrolyte, such as seawater, which is why it’s used in sacrificial anodes. Zinc, however, also imparts strength to copper, mixing the two, often in about a 40-60 ratio respectively, results in a brass suitable for clocks, lamps and cabin hardware, but most definitely not, with few exceptions, for seawater plumbing.
Copper-zinc alloys used below the waterline undergo a process called dezincification whereby the zinc corrodes from the alloy, leaving behind a pink, porous and very fragile structure that’s almost certain to fail. For the most part, true bronze alloys are zinc-free, their primary elements being copper and tin. Other alloying elements include silicon and nickel (technically making them something other than bronze, but still acceptable for use in seawater plumbing). These are the best alloys for use below the waterline because they are not susceptible to dezincification
Unfortunately, a huge range of alloys lies between true bronze with no, or very little zinc and true brass which contains a high percentage of zinc. Two common alloys often used in marine applications are 85-5-5-5 (or C83600) and DZR.
85-5-5-5 contains 85 percent copper, 5 percent zinc, 5 percent lead and 5 percent silicon and can be used below the waterline.
Some European manufacturers use something referred to as DZR brass, a dezincification-resistant brass alloy. This alloy has a higher zinc composition than many other copper alloys (30 percent or more), but it also includes trace amounts of other metals meant to retard zinc corrosion or leaching.
Neither of these alloys resists dezincification nearly as well as the zinc-free or near-zinc free bronze alternatives; but as they are less expensive and unlikely to become a problem in the early years of the boat’s life, they can be an attractive alternative for more cost conscious builder.
