VicS
Well-Known Member
Bronzes are alloys of copper and tin containing little or no zincI am in a similar position, but with a bit more anode I think (hope)
When the anodes are gone you start to get problems with your props, possible the rudders and P brackets too. The zinc starts to come out of the bronze alloy and weakens them. If ordinarily on your berth, your anodes last a decent length of time, then this is is not a fast process. It takes many months. If you are in fresh or brackish water - again it is slower. If the props and metal work have been antifouled with some sort of paint this also slows the process down. I wouldn't panic yet, and to be honest there is nothing you can realistically do right now.
Next time the boat is out have a good look at the props after they have been really well cleaned and look for salmon pink spots or pink edges. If there are any, see if they will just polish out with a bit of emery cloth. Give the edge of the blades a gentle tap with a small hammer or the flat of a spanner in a few places - they should make a nice "ting".
If the damage is bad a prop shop will probably able to restore them by brazing in fresh metal. Hopefully we can all get moving again in another 6 - 8 weeks so your boat should be fine. Don't worry.
The exception is so called "manganese bronze", which is really a brass, but it is corrosion resistant, making it a good choice for propellers, and therefore does not need the protection of an anode