Metallurgists - what screws to use.

[mlines]

I have a standard galvanised(?) trailer and use it to launch into sea water.

I am fitting a hub flushing kit and it has an inlet fitting that requires screwing to the trailer chassis. The fitting itself is plastic so not an issue. However I need to drill the chassis and screw fit the fitting (unless there are other fitting recommendations??).

I do not want this to rust out within a short amount of time, either the drilled holes where it has broken the galvanisation, the screws themselves or through galvanic reaction (screw metal to chassis metal)

What does the panel recommend?

Martin

 

[Beamishken]

It's usually a hosepipe fitting can't you just use large plastic tie wraps to secure it somewhere convenient

 

[mlines]

It is a hosepipe fitting, with a screwmount base. I could use cable ties, but that ends up looking like a bodge with cable ties

 

[GrahamHR]

My Alko kit came wit a plated bracket that the hose fitting is attached to. I made up a plate from an offcut of thick polycarbonate and clamped the two plates to one of the trailers box section using long bolts and nuts. No drilling of the trailer needed.

 

[Bertramdriver]

Buy stainless steel tie wraps from ebay. Cheap as chips and worth their weight in gold.

 

[Momac]

Nylon ?
http://www.componentforce.co.uk/category/406/hex-head-screws

 

[jfm]

I think you're over worrying! galvanic action will not be big because the time spent immersed is too little, especially if you hose the trailer with freshwater. also don't worry about small breaks/scratches in the zinc galvanised coating

I would just use s/s screws. Drill and tap M5 or something I guess, or maybe even self tappers. I would insert them with plenty of grease, and just not worry about it. Ok so if they go a bit bad after 5 years you can remove them and increase the M5 to M6 and you're good for another 5 years!

 

[Assassin]

Stick to drilling and tapping and using mild steel bolts, if you put stainless steel fastenings into a galvanised mild steel trailer you will get electrolytic reaction.

You can get cold galvanising sprays to spray the bolt heads and these are very good.

 

[TQA]

Definitely not stainless.

Galvanized if you can find them.

Next best would be mild steel and paint with zinc rich primer.

 

[vyv_cox]

Stainless steel bolts will not be a problem. There will be some galvanic action between stainless steel and the mild steel of the trailer, in which the mild steel would be preferentially corroded. However, the mild steel is enormous by comparison, so the rate would be very low, particularly as already pointed out, where the immersed period is very short.

So far as the zinc galvanising is concerned there will be minor loss but its rate will be very low. I use a stainless steel shackle between my galvanised anchor and galvanised chain. I anchor a great deal, most nights for half the year. In five years the zinc on the last three or four links of the chain has been partly lost, no rusting.