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**GordMay** · 25-01-2006, 04:00

The terms Brass and Bronze are highly imprecise, which do little to describe a material's properties, beyond the very basic and incomplete:
Both Brass & Bronze are “Copper Alloys”.
"Brass" is Copper and Zinc.
"Bronze" is Copper and Tin (Or not zinc or nickel).

There are around 370 commercial compositions for copper alloys*. All copper alloys resist corrosion by fresh water. Copper nickels, aluminum brass, and aluminum bronzes provide superior resistance to saltwater corrosion.

* See the ASTM Standard Designation for Wrought and Cast Copper and Copper Alloys:
http://www.copper.org/resources/prop...roduction.html

Michigan Wheel Corporation typically uses ”Manganese Bronze Michalloy K”*, for it’s sailboat propellers; although “NiBrAl Michalloy XX” (Nickel, Bronze, Aluminum) material is also available.
http://www.miwheel.com/

* ‘Michalloy K’ is a proprietary alloy, for which I can find no definitive information.

Michigan Wheel Corporation
1501 Buchanan Avenue SW, Grand Rapids, MI 49507
Phone: (616) 452-6941
Fax: (616) 247-0227
E-mail (For General Information): info@miwheel.com
Dealer locator: http://www.miwheel.com/MIWheel/Deale...or/default.asp

Richhh · 25-01-2006, 06:07

If your prop is truely brass (various mixtures/alloys of copper and zinc) be prepared to accept some corrosion of the prop when using a zinc anode, as the prop will most probably 'de-zinc' along with your zinc anodes. The electro-chemisty of corrosion doesnt care where its maximum potential is located (on a boat). What you will notice is that the 'brass' will become 'more red' as time goes on as the zinc composition is removed from the prop. A magnesium anode would probably be more proper for protection of 'brass' components. And of course such anodes must be properly electrically bonded to what you intend to protect.

Its noteworthy that many 'cheap' bronzes can be found on boats that contain small amounts of zinc. In the 'trade' these so-called 'bronzes' are called red brass and are quite inferior with respect to galvanic corrosion due to their inclusioin of zinc content. The zinc is added to make the bronze 'free machining' - easier to machine and form. Probably the best 'bronze' for seawater service is Nickel Aluminum Bronze (developed by AMPCO Metals Inc.); and, was adopted by the USN in the late 50s early 60s as the 'standard' bronze - very expensive and a 'bitch' to machine.

You can 'try' to protect a brass component with a zinc anode but its probably 'wiser' to use a magnesium anode and insure that that anode has a very good electrical 'bond'.

Matt Hager · 25-01-2006, 07:59

last summer I learned about Prink Brass/Bronze. As I am sure everyone nows that if there is a pink color in the Brass/Bronze it junk, toss it and replace it.

Jentine · 25-01-2006, 15:46

your bronze propeller will be just fine. If what you say is true, that it was made by Michigan Wheel, their website states that the following:

Our 2-blade and 3-blade fixed pitch propeller series for sailboats are available in diameters of 10" - 24", in a wide range of pitch. Custom sizes are also possible. The typical material is Manganese Bronze Michalloy K, although NiBrAl Michalloy XX (Nickel, Bronze, Aluminum) material is also available.

**irwinsailor** · 25-01-2006, 16:22

I know that it is brass. They may not make brass props anylonger but this one is still brass. From what I have gathered in this thread it will not be a big problem. If it last 5 years I will be more than happy. I would like to replace it with a folding prop one day anyway. I read all the time that a folding prop is good for reverse. My boat has prop walk that is unbelievable!