Threaded steel outdoors

We are doing something with long steel rods which will be threaded at each end. Unfortunately, the length we need they can't source in stainless. Most of it will end up inside but the threaded part and nuts will be outside.

Is there any treatment I can use to stop the threaded end rusting? We don't anticipate ever needing to undo it but you never know and if it rusts the nut will be a right pig obviously!

d000hg said:

the length we need they can't source in stainless

Click to expand...

what length is it? What diameter?

how much will be outdoors?


What will it be?

Just a few inches each end will be exposed eventually, though initially all of it will as there is a cover to go on. It's 12mm steel being used along the same principle as strapping to hold two brick walls together that are trying to fall apart. It'll go (I'm told) through both walls with a plate on the outsides.
Over 5m lengths but it's already ordered either way.

Can I just paint the threads or will that only cause the same problems as rust if I ever want to undo it?

galvavised rod indoors



threaded connector

or

stainless rod outside



Another method is to use sleeve nuts on the outside. The sleeve penetrates through the plate and encloses the rod inside. It gives extra protection to the screwed joint because it is closed at the end, and the long sleeve gives more protection. You would need a stainless lube/anti-seize because stainless is prone to cold-weld and become unmovable. The compound looks likre grease but is based on clay.



you might benefit from an extra-large or flanged head on the sleeve nuts or an extra-long sleeve, but you can paint that part of the rod that does not screw into the nut (the nut will tend to scrape off extra paint) The size you want may be available from a stainless stockholder, it is probably Architectural ironmongery or marine.

You could also use a stainless domed or acorn nut, after trimming the rods, they have a closed end to keep the weather out and look neat.

If you end up with galvanised, use a ceramic grease generously on the threads.

We used to use copper grease, but it causes galvanic corrosion over time.

Cheers John. We did consider connectors but the guy doing it didn't seem keen and it's on order now so we'll go with it. Thanks for those fixing ideas they both sound good. To make sure I've understood:

• Sleeve nuts would go through the plate and brick - so we make a slightly bigger hole - and mean there is no exposed metal to rust, and I'd need anti-seize.
• Domed nuts are fairly self-explanatory, but these would use regular ceramic grease... or do they need anti-seize as well?

They both look like they'd give a good appearance.

AFAIK stainless steel rods aren't available in high tensile (surely required for a job like this?). High tensile steel used for exterior strapping/tie rods has generally been hot dip galvanised, not electro plated which won't last in exterior conditions

Just thinking aloud...

If the guy doing the work would rather use standard nuts than domes, would plastic dome covers suffice?

https://www.boltandbearing.co.uk/02nccb20

An advantage is that he can fit the nuts and then trim the excess rod way, giving him more wriggle room when tightening than would be the case if using dome nuts.