Corrosion?

[BlueYonder]

This picture is from a boat on the hard in my marina. I pass by it on the way to my boat and have noticed that the props almost look rusted.

 

[boatpoker]

That looks more like calcereous build up rather than corrosion as the "bumps" stand proud of the surface.

Most propellers are "manganese bronze" which is misleading as mb is actually a brass due to it's high zinc content. Manganese bronzes typically show corrosion with pits and a pinkish hue due to dezincification.

PS. The jam nut in your photo is in the wrong place, it should be against the prop hub.

 

[ulysses]

Boatpoker stated it very well as to the metals and the jam nut. What he missed is that it seems to be missing a rudder.

 

[boatpoker]

Boatpoker stated it very well as to the metals and the jam nut. What he missed is that it seems to be missing a rudder.

Betcha there's one there somewhere

 

[Ski in NC]

When zincs are working, the prop becomes the cathode and is actually "electroplated" with whatever minerals are in the seawater. Makes a skin of whatever, but metal below is still ok. Color of coating depends on what is in the water.

I try to scrape the skin off my prop when I dive on it, it is a yellowish white here and tough as nails. PITA.

That pitting in the pic might have happened while on the hill.

 

[FF]

Its new props time when they turn PINK.

 

[Capt.Bill11]

Yeah but it's not pink. Just covered in mineral build up that happens to be reddish colored.