Fastener Corrosion

[Phosphor]

Hello. My friend and I are working on a Parker River Turnabout and I'm a bit confused on how to tell if our fasteners are shot. I picked it up about 2 years ago from a guy who picked it up from someone else so I have no idea of the date of the origin of the boat. The fasteners are a bit corroded on the outside. I know they're not steel, my next guess would be something copper based. The corrosion is a red dust that built up on the outside. Is there a way we can tell if it is ruined throughout the thread and shank without removing it? Thanks!

[lewisboats]

Run a magnet over it to see if it is ferrous. They are possibly galvanized Iron. Copper based stuff usually corrodes green ish. To me red dust means rust, which means steel or Iron as the major component. You will probably have to remove a few of the worst looking specimens and determine the condition of the rest from there...a guess at best.

Steve

[Phosphor]

We determined that it's definitely copper. After scraping away some of the corrosion we saw copper metal. I'm just rather surprised it wasn't a green patina. 'Tis very strange. Some of it's red dust, but none of it is green...

[SailDesign]

Probably a bronze - I cannot remember if it is Silicon, Aluminium or Phosphor Bronze that turns red when it corrodes.... Ironic if it's Phosphor, though :)

Steve

[Robert Gainer]

Copper is alloyed with zinc to make bronze and the zinc will leach out of the alloy to leave raw copper in the right (maybe wrong is a better word) conditions. The result is metal that is pink or red in color and is granular in texture and tends to crumble when you poke at it.
Robert Gainer

[Phosphor]

That is exactly what we are hitting. Thank you! We are also seeing the green patina now on the shank of the screws, especially where they were buried into wet wood.

[gonzo]

Brass will loose zinc by electrolisis and get a red dust if it corrodes in low oxigen conditions. The usual procedure is to remove two fasteners forward, two in the middle and two aft.