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Henning 4148
10-04-2009, 02:09 PM
This weekend, I have been looking over the mast of our new used boat. Not to bad all in all, but I need to reattach the spreader bases to the mast. They were riveted, but had worked themselves pretty loose already. The spreader bases are made from shiny heavy plate, I assume stainless, the mast is Al. What material should the rivets be? Monel ? Anything else to watch out for? Some goo around the rivets between the surfaces (there wasn't any)?

John Meachen
10-04-2009, 04:01 PM
It used to be quite easy to get hold of zinc chromate paste to use as a barrier between dissimilar metals.Monel rivets would be my choice.

Bruce Hooke
10-04-2009, 05:33 PM
Since the fitting is presumably stainless steel and since stainless steel and aluminum are pretty close to each other on the galvanic scale, it seems to me that stainless steel fasteners ought to be a perfectly reasonable solution. As Feazer noted, you don't really want something more noble than stainless. You also really don't want something that is less noble than aluminum...you really don't want those fasteners giving out! Much better to loose a little mast over time than loose the fasteners since the mast is a much larger chunk of metal. The only metals I see on the galvanic series between stainless and aluminum are cast iron, wrought iron and mild steel, all of which have obvious problems!

Sure you can try to insulate the mast from the fitting and fasteners, but it is likely to be hard to do effectively, isn't it? So, my inclination would be to go back with stainless steel fasteners. HOWEVER, I make no claim to being any sort of expert on this question! I am just trying to apply logic (and the galvanic series), which can sometimes lead one astray...

martin schulz
10-05-2009, 08:43 AM
The best one can use against rot is definitely white lead paste.