Brass screws on bronze

[JustMelfort]

I have a fibreglass hull and wooden rudder. All less than 9 months old. The rudder hing and fittings look to be brass - so assume they're bronze, but I think the screws holding the rudder fittings are brass as fittings are going pink as they age. Does this matter? Do I need bronze screws? I guess SS is no use. Grateful for your thoughts.

 

[burgundyben]

You dont say if the fittings in question are under water?

If they are submerged then they should be bronze and if in any doubt then swap them for items you know to be bronze.

 

[Peterduck]

Turning pink is a classical symptom of brass. It is the process of de-zincification, where the zinc component is dissolved, leaving a weak, spongy copper behind. Replace with silicone bronze ASAP or earlier. Stainless is definitely not the go in this situation. A big trap in this situation is "Manganese bronze", which is not a bronze at all, but a brass.
Peter.

 

[JustMelfort]

They're not underwater but on the hinges just above the waterline so they get pretty soaked the whole time under way.

 

[JustMelfort]

Sorry Peter - may be being dense - but its the hinges going pink, not the screws. Are you meaning that the hinges could be brass or manganese bronze?

 

[Peterduck]

Yes, it certainly sounds that way. Brass, in its unweathered condition is a very pale yellow, while bronze is more toward an orange kind of colour. If you take to the fittings with some emery cloth, you should be able to abrade down to the unweathered metal if the de-zincification hasn't progressed too far. The boat's builder may have assumed that it would only be used on lakes and not saltwater, and fabricated the fittings from sheet brass.
Peter.