screws and rust query

[jaybeegee]

please see link IMG00002-20110326-1206 | Flickr - Photo Sharing!

Very surpised that these screws have rusted in this manner! Is there a particular type or attribute for the screws that I should ask for when replacing?

Also any recommendation of an inexpensive product to remove the rust marks available from a DIY? I was told toilet bowl cleaner - any comments?
cheers
J.

[mdbee]

Are you sure it's from the screw? Looks like some rust above. May have run down?

[r.furborough]

It's not just the screw, I think the bracket was either not mounted using a sealant or the sealant has failed. I think the evidence of rust points to crevice corrosion between the bracket and fiberglass.

[jaybeegee]

Originally Posted by r.furborough

It's not just the screw, I think the bracket was either not mounted using a sealant or the sealant has failed. I think the evidence of rust points to crevice corrosion between the bracket and fiberglass.

Thanks for your prompt replies!

So I will remove the whole unit and double check if the source is the screws.

Need some spoonfeeding regarding the sealant ... where should it be used? Is it the washer between the ladder chrome frame and the hull?

Also, is the toilet bowl cleaner an option for removing this type of rust?

thanks

J.

[Perithead]

Here is an EXCELLENT thread about sealing hardware. I haven't tried the method yet, but my butyl tape is on it's way via the USPS.

http://www.sailnet.com/forums/gear-m...utyl-tape.html

[sea_hunter]

Originally Posted by jaybeegee

Thanks for your prompt replies!

So I will remove the whole unit and double check if the source is the screws.

Need some spoonfeeding regarding the sealant ... where should it be used? Is it the washer between the ladder chrome frame and the hull?

Also, is the toilet bowl cleaner an option for removing this type of rust?

thanks

J.

Sikaflex 261 or 3m 5200 as a sealant. Don't use CLR or any acid (naval jelly) on fiberglass. Some metal polish and a scotchbrite pad will get rid of most of it.

[mitiempo]

Don't use 5200 unless you will never remove the item. If you try it often pulls gelcoat with it.

Sika 291, butyl, or 4200 (which is still more of an adhesive than you need) are better choices.

[CorneliusSneed]

I see three possible sources for the rust. The shoulder (or interior) of the socket around the bottom of the tube, the bracket itself, or the screws. I am curious as to the composition of the screws, the socket, and the bracket. It seems to me that the rust trails are coming from beneath the bracket, though I could be wrong. The bracket, however, looks like proper brass to me, which could not cause the rust, in which case the screws would be my main suspect.

Also, there seems to be a rust buildup in the slot of the screw, though that could, of course, merely be a stain.

I would be interested to know what you find out. I am betting your first impression is correct, in which case brass screws would be your best bet as a replacement, I think. Stainless is not all it is cracked up to be, especially if you are sailing in salt water.

[mitiempo]

The bracket looks like stainless to me. brass by the way should really not be used on a boat except to hold brass interior lights up. Bronze wouls be the correct choice were the bracket not stainless. The fasteners are probably 18/8 stainless. And stainless does rust. There are very good cleaners to remove it.

[CorneliusSneed]

Originally Posted by mitiempo

The bracket looks like stainless to me. brass by the way should really not be used on a boat except to hold brass interior lights up. Bronze wouls be the correct choice were the bracket not stainless. The fasteners are probably 18/8 stainless. And stainless does rust. There are very good cleaners to remove it.

Yeah, the bracket could be stained stainless, or it could be oxidized brass. Hard to tell, really, from the pic. Regarding brass vs. bronze, I agree bronze could be a viable alternative, however, there is a long maritime tradition of brass fittings on ships. The difference is in whether the copper is alloyed with zinc, or tin. Both oxidize, neither rust. And I have never seen a bronze screw for sale, though it could be that I have merely missed the proper hardware stores.

Nice call regarding screws vs. bracket, as far as metals go. Many people don't take electrolysis into account.