Corrosion problems with hull fastenings

[Seagreen]

I've found that one or two copper or silicon bronze boat nails in my planking have degraded a great deal, since being near a concrete and scrap iron mix in the bilges. Is this problem going only to be local to a fastening being too close to scrap iron, or will the entire bilge need to be cleaned of concrete/scrap iron and suspect nails replaced? I should say that the hull is aged 1" pitch pine planking on oak frames.

 

[ccscott49]

Might well be localised, but would you like to take the risk, I'd have it all out and refasten where ness, but if you can see them from the outside, maybe just put somemore fastenings in?

 

[Transcur]

You havent indicated what age the fastenings are. I am in the process of refastening a boat below the water line only 60 years old. Some of the coper nail heads had corroded to nothing. The first indication things were wrong was when on cleaning the hull inside the rooves popped off and tell tale red powder showed. The fastenings were worse on the garboard adjacent to the iron keel. Obviously some had been weeping around the poorly corroded fastenings. Safest and best solution is to remove and replace all fastenings below water line, only 1700 in total(1100 to go)!! Those above waterline were fine.

 

[Seagreen]

The age of the fastenings varies. There are some bronze boat nails that are in mint condition, but some copper ones that may be about 30+ years old which are in close proximity to scrap iron in the concrete - its these which have gone, but only a few. The boat was originally fastened with iron nails about 150 years ago, but most of these were removed in a major rebuild 20 years ago and replaced with the bronze and copper, most of which seem sound. The remnants of the odd iron nail causes local corrosion but are not structurally significant. The boat itself actually leaks very little, except when the keel is massively stressed in a rolling beam sea!

The exposed top of the keel and garboards are generally in very good condition, in fact, excellent for the age of the boat.