silicon bronze screws ?

[Marty D]

Im replacing the trim taps n was going to use S.S. screws but was told silicon bronze screws are better. Did anyone ever use them for under water ? Are they strong as SS. ?
3 of the SS screws broke trying to remove them. You can see they were pitted. This could be because there were no zincs on the tab plate. I will installed zincs. Should i paint the tabs ?

 

[DaleH]

Bronze is far more 'noble' and is superior to SS when fully immersed in saltwater, but whereas the SS screws for trim tabs on Parker hulls only hit fully frp layup, SS fastenersare fine.

FWIW I've tried 5-different paint/wax/other methods, less coating them with epoxy-based expen$ive barrier coat 1st ... and I've to find ANYTHING last a season even w/ anodes on the tabs.

 

[Marty D]

Bronze is far more 'noble' and is superior to SS when fully immersed in saltwater, but whereas the SS screws for trim tabs on Parker hulls only hit fully frp layup, SS fastenersare fine.

FWIW I've tried 5-different paint/wax/other methods, less coating them with epoxy-based expen$ive barrier coat 1st ... and I've to find ANYTHING last a season even w/ anodes on the tabs.

Yes your right. Im thinking to just mount zincs n leave them SS without paint. They will get dirty but that will be better then sanding n repainting every year. The tabs willnot rust ?? Im not getting what you said ''but whereas the SS screws for trim tabs on Parker hulls only hit fully frp layup, '' ??
You are saying SS are ok to use but why ????
Did you get the shims ?? i sent them tuesday.

 

[sparky]

Stainless steel screws in an oxygen-free environment (anything sealed from the water) will not be able to passivate, and will erode like iron fasteners.

If there's free-flowing water around the fastener, it will passivate (make an inactive oxide layer on the metal), and be protected. If the fastener goes into the FRP (where there is no oxygen), they will deteriorate. Silicon Bronze is far superior below the waterline, and is available from Jamestown Distributors, McFeely's, and Defender.

Google "Crevice Corrosion Stainless Steel" for more info.

Read this: http://www.alberg30.org/maintenance/Ste ... Corrosion/

And this: http://marinesurvey.com/yacht/corrosion_1.htm

 

[Marty D]

Stainless steel screws in an oxygen-free environment (anything sealed from the water) will not be able to passivate, and will erode like iron fasteners.

If there's free-flowing water around the fastener, it will passivate (make an inactive oxide layer on the metal), and be protected. If the fastener goes into the FRP (where there is no oxygen), they will deteriorate. Silicon Bronze is far superior below the waterline, and is available from Jamestown Distributors, McFeely's, and Defender.

Google "Crevice Corrosion Stainless Steel" for more info.

Read this: http://www.alberg30.org/maintenance/Ste ... Corrosion/

And this: http://marinesurvey.com/yacht/corrosion_1.htm

Thats why my SS screws were getting bad, I been putting bottom paint over the screws heads every time i paint the boat. Im going to use silicon bronze screws because i cant tell the guy who paints my boat not to hit the screws;.
Thanks Marty