Thread: What's the best corrosion resistant bolt?

Can you get 1/4 inch gal bolts or will they just be zinc plated?
You better check whether you need 1/4 in or 6 mm

I still think your best option will be a standard black bolt with a dollup of bitumen on the mating surfaces in the vicinity of the bolt hole, with the exposed portions of the bolt coated in "goo"

after all, you're back filling behind the wall and filling the pool with water so the application is hardly "structural"



ian

Originally Posted by ian

Can you get 1/4 inch gal bolts or will they just be zinc plated?
You better check whether you need 1/4 in or 6 mm

I still think your best option will be a standard black bolt with a dollup of bitumen on the mating surfaces in the vicinity of the bolt hole, with the exposed portions of the bolt coated in "goo"

after all, you're back filling behind the wall and filling the pool with water so the application is hardly "structural"



ian

The bolts are definetly structural- if they fail, the walls will most probably collapse as they are nearly all that holds the wall together.
I think he said he would be supplying galvanised bolts and he will throw in some epoxy to paint on them as he had done for another customer. I just need to be sure that
it will work in the longer term?

If I've got the situation right
you've bought an above ground pool
the sides are fibreglass held together with 1/4in x 1-1/2 in bolts
the pool uses a vinyl liner to kept the water in it
you intend backfilling behind the pool, probably after you fill it, converting the pool to an inground one.
hence the force that would lead the walls to collapse (the water in the pool) is mostly supported by the back fill behind the fibreglass walls
the bottom of the pool is on the ground, held there by the water in the pool – unless your land subsides, the bottom of the pool is going nowhere

It would be a different story if the pool sides were unsuported by backfill, but in this situation you would not be so worried about corrosion



ian

[quote=ian;829502]"If I've got the situation right
you've bought an above ground pool
the sides are fibreglass held together with 1/4in x 1-1/2 in bolts
the pool uses a vinyl liner to kept the water in it
you intend backfilling behind the pool, probably after you fill it, converting the pool to an inground one.
hence the force that would lead the walls to collapse (the water in the pool) is mostly supported by the back fill behind the fibreglass walls
the bottom of the pool is on the ground, held there by the water in the pool – unless your land subsides, the bottom of the pool is going nowhere
It would be a different story if the pool sides were unsuported by backfill, but in this situation you would not be so worried about corrosion"




No, its an in-ground pool and its not bought yet.
It has no bottom, except for the liner.
I need to ensure these bolts, which will hold the walls together, will not fail, so I have very good reason to be concerned about corrosion- its a bolt together pool after all.
If a pool has no water then the walls can collapse from the pressure of the backfill soil as well as from the pressure outwards, of a pool full of water.

I would contact your local water board/authority and see what they use on there mains underground as far as bolts go. Other than that it sounds like a nightmare of a pool, why not buy a standard fibreglass in ground pool, they would be a lot less trouble and are not all that expensive.

Originally Posted by Claw Hama

I would contact your local water board/authority and see what they use on there mains underground as far as bolts go. Other than that it sounds like a nightmare of a pool, why not buy a standard fibreglass in ground pool, they would be a lot less trouble and are not all that expensive.

reckon the cost alone, of transporting a full fibreglass pool to where I am, would be about the cost of this sectional pool. I have looked into all the options and this is the only viable one, thanks anyway.

Too much intrigue, where are you Stan?

Originally Posted by Claw Hama

Too much intrigue, where are you Stan?

No there's no intrigue, I just want to find a bolt that will last in this application- I dont think my address is relevant to that.

Yes, a galvanized bolt/nut assembly coated with epoxy will do a fine job of keeping moisture off the fastening system. Be liberal about coating and consider multiple coats, as the thicker the coating, the better and the more likely you'll not miss a spot.

Originally Posted by PAR

Yes, a galvanized bolt/nut assembly coated with epoxy will do a fine job of keeping moisture off the fastening system. Be liberal about coating and consider multiple coats, as the thicker the coating, the better and the more likely you'll not miss a spot.

Many thanks PAR, you have been very helpful with your advice and I think the
problem is now solved.

Originally Posted by PAR

Of course the kicker is if you miss a spot with the tar and a fastener lets go at a bad time (like when the pool is full of lawyers and politicians, during an election year). You may end up with more then a soggy back yarrd.

How's that Brad?

It is sometimes hard to see any disadvantages with such a comprehensive view of the situation.

You have excelled yourself Paul.

MIK

Originally Posted by Vernonv

Won't you have trouble putting the nut on the bolt if it is covered in bitumen (or it will just strip the bitumen off)?

Vernonv, the idea of heating up the metal is to let the bitumen soak in to the pores of the galavanising and seal it. The resultant coating is in fact quite thin and does not affect the threads much.

Rhys

The best material you can use in contact with saline water (lifetime guarantee) is of course Titanium metal. Although fairly expensive, they are available - just do a google search. Titanium metal is used in industry especially in contact with chloride (eg sea water - sodium chloride). It has very high tensile strength as well. As an example of its use in a similar environment, the Chair Lift at Arthur's Seat on the Mornington Pennisular Victoria use them to bolt down the posts. As many of you might be aware, some years ago their was a accident here when one of these posts gave way and 2 people fell and were severely injured. Apparently, the original stainless steel bolts, over time in this marine environment, suffered from minor corrosion but enough to cause fatigue in the bolts and they sheered off. All these bolts have now been replaced by titanium ones.

The reason titanium works so well is that unlike other metals it reacts very quickly with oxygen in air to form a very thin (5 microns) layer of titanium oxide (basically a ceramic). This layer is very stable and impervious to attack by salt water.

Hope this helps

Titanium is a lovely metal though cost prohibitive to the common man generally. Stainless suffers from a number of issues, depending on what type, loading cycles and environment. Previous corrosion is a common problem, particularly with the harder versions of stainless. The Mornington Pennisular Victoria incident was a result of this issue and one that is very difficult to pre-diagnose. The only real cure for it is scheduled replacement well under it's cyclic threshold. In a buried set of fasteners, not a probable solution.

The use of an inert coating (epoxy) over galvanized, mild steel will prove the most reliable and cost effective method, from both a engineering point of view and when looked at with economics in mind.