Rusty rivets on mast

[seaangler23]

About to drop the main on my boat for new standing rigging and furler, I’ve noticed rusty mild steel rivets holding on various furniture on the masts mainly the Gibb shroud sockets and mizzen shroud plates, should these not be stainless? My impression it was either stainless, alloy or Monel fastenings on masts? Either way they need replaced

 

[Old Bumbulum]

Never heard of mild steel 'rivers'! They are almost always aluminium alloy of some ilk thought stainless ones are available they can be a pig to use as they are so hard. Might the rust be due to the head of the mandrel (shank) left in the rivet after it has been set - which is steel?
ps. Monel is an alloy...

 

[seaangler23]

Autocorrect!
nope definitely steel, not a rust stain the entire heads are corroded,

 

[Daydream believer]

I think they are called "bulb tight" pattern used on roof sheeting as they are supposed to prevent leaks. I used them on coated steel roofs years ago. But as far as I am aware they are all alloy now. The last sheeting we did was screwed.

 

[macd]

ps. Monel is an alloy...

I fear you're wasting your time, Bumble, as #4 confirms. (Although I agree, so you could possibly call me an ally )

 

[Bobc]

I had a few rusty rivets, and it turned out to be the mandrels rusting which hadn't been pushed out when the rivets were put in.

You should probably replace them anyway, just for peace of mind.

 

[seaangler23]

Sorry aluminium alloy if it wasn’t obvious enough ?

 

[seaangler23]

I think they are called "bulb tight" pattern used on roof sheeting as they are supposed to prevent leaks. I used them on coated steel roofs years ago. But as far as I am aware they are all alloy now. The last sheeting we did was screwed.

From the size of the heads that may be what they were designed for, they look more like button head Allen bolts than rivets due to the size and shape of them