Input on identifying ship (boat) propeller shaft material

[keeena]

I've been gifted some metal and wanted to know more about it. I was told that this is a section of ship propeller shaft; its about 60mm (2.375") in diameter. It clearly looks bronze-ish. Some quick searching showed that there are some specific bronze alloys that are sometimes used for ship shafts; manganese bronze and nickel aluminum bronze were a couple I found.

I'm just curious if anyone could help confirm or if there's a way I can make a better guess. I realize metallurgical analysis is the only sure way to identify.

I was planning on using to make plain bearings. There are some very significant property differences as compared to typical bearing bronze (tin-bronze alloy); particularly a LOT higher tensile strength. But I'm expecting it would be fine for non-critical, garage hack-machinist stuff. So any input for application & machining: I'm all ears. I don't expect I'll ever weld/braze it.

 

[woodchucker]

well, I'll be right up, cut me a piece off, and I'll play with it a while and let you know what I think .
That's a huge chunk. Cool stuff.

 

[Ischgl99]

That's a nice gift, I need friends like that lol.

You may have found this already, but Kloeckner Metals has this description on their website with a few standard grades. Maybe machine the end and see what the color looks like and see if the grades below match up with a color in the bottom chart?

Marine Grade Bronze​

Finally, among bronze alloys, those alloyed with silicon like C65500 and aluminum like C95400 are better able to resist the corrosive effects of marine environments. In fact, aluminum bronzes and silicon bronzes were created precisely for marine use. Another grade that’s suitable for marine applications is C51000, which is alloyed with phosphor.

Like copper, bronze alloys also fight off algae, mussels, and other disruptive organisms. Marine grade bronze finds its way into marine fasteners and pipes. Because it produces little friction, it’s also popular material in propellers and propeller shafts.

Bronze​

Bronze is an alloy consisting primarily of copper combined with other metals like tin, aluminum, manganese, and nickel. Here are some common bronze types and their colors:

Bronze Type	Metal Composition	Color
Statuary bronze	97% copper, 2.5% tin, 0.5% zinc	Warm brownish red
Aluminum bronze	95% copper, 5% aluminum	Golden yellow
Nickel bronze	89% copper, 10% nickel, 1% zinc	Pale gold
Manganese bronze	58-63% copper, 35-40% zinc, 1-3% manganese	Golden brown
Silicon bronze	96% copper, 3% silicon	Warm yellowish brown

With bronze, small percentages of metals like tin, aluminum, nickel, manganese, and silicon blended with copper create an array of golden brown, brownish red, and pale gold colors.

 

[matthewsx]

I have a bunch of what I suspect is prop shafting since the guy that gave it to me had a house overlooking Opal Cliffs in Santa Cruz.

Most probably Aluminum Bronze and should be fine for whatever bushings you need to make.

John

 

[keeena]

Thanks for the color chart @Ischgl99. I lopped off a piece for a project. To me it looks golden yellow; possibly between golden and pale gold. Considering that and the supposed source/application: gonna call it aluminum bronze for now To my untrained eye it almost looks like brass after turning. But the chips are well formed 6's as opposed to the gold dust that brass tends to make.

A follow-up question: I had to turn a good 0.150-0.175" off to get under all the corrosion. In places it could almost be chipped off (like the candy shell on an M&M; didn't taste as good tho). The corrosion was much deeper than the candy shell. It sounded rough to turn off and resulted in a brown-pink dust & very small chunks like coffee grounds. The dust was a pain to clean off the lathe. Best I could tell in some searching is Bronze Disease corrosion. Once underneath all that: turned nicely.

Figure I'd add in case it helps w/ identification or mystery.

Candy shell


Turned quite a bit to get under the corrosion

 

[matthewsx]

Looks like what I have, minus the corrosion. Mine has just a thin layer of oxidation since it’s never been used (pretty sure it’s offcuts from a boat builder).

John

 

[keeena]

This stock had a couple very obvious wear points where it necked down and diameter was notably smaller. If you look at the pic in the first post near the floor you can see a bit of an hourglass shape. I could imagine the wear was from a guide/bushing/seal. Whatever it is: this certainly has some miles/age.

 

[Ischgl99]

I would agree that it is probably aluminum bronze. I didn’t realize bronze would corrode that deep like that, at least the stock is large enough that there is enough useful material left. Before using it for anything important, you might want to check the worn area for cracks, since it was used as a propeller shaft, it had a lot of cyclical stresses and could have small cracks in that area.