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need some concrete bolts (the screw thread type, not sleeve anchor things) for outdoor use to fix down some fence supports, whats the best corrosion resistance?
choices seem to be Zinc plated, Bright zinc plated or yellow zinc plated?
Some sites say bright and yellow not suitable for outdoor, others say theyre fine use so not sure what to get!
I am no builder/expert but I don’t find zinc plating lasts that well outdoors. I try and get galvanized when getting outdoors bits (gate hinges etc) as it lasts way longer.
as soon as you use them the zinc will start to go rusty. i would use galv for a fencepost. or BZP if not available. I dont think there is much difference between yellow and BZP
cant seem to find any galvanised ones in screwfix or toolstation, but toolstation do Zinc flake coated which is apparently much better than zinc plated so ill try those.
Im using concrete bolts instead of sleeve anchor things as they are supposed to spread the load better and are better for placing near the edge of concrete than the expansion type, is this correct? - its for fencing on the edge of a concrete slab
How close to the edge of the slab are you drilling? Any danger of the slab blowing away? Are you talking about Thunderbolt -type bolts over Rawlebolt -type fixings? are you fixing metpost type fittings to the slab?
What diameter and length are you using ?
What edge distance are you looking at ?
As far as corrosion goes , the levels would be
Zinc Plated (poor external)
Zinc Flake Coated ( good external)
Hot dipped Galvanised. ( great external)
The ones from toolstation would be good enough for what you want to use them for IMO
If you have time to get them then are a few different brands you can use.
JCP Ankerbolts (my preferred choice but I normally use M16 diamter)
Thunderbolts
Forgefast lighting bolts
If you're near the edge of a slab, use the resin fixed type. Drill the hole and glue the bolts into them. You can get stainless bolts for those.
Actually I think I might be a bit close to the edge so am going to swap the concrete threaded holds for threaded rod and resin fixing.
How do you get all the concrete dust out of a vertical downwards hole before putting the resin in, I'm guessing a brush won't work as well on a vertical hole? Can I wash it out with a hose pipe nozzle, and then would I have to wait until the hole is completely dry before using the resin?
Use a pump with a tube on the end. Fairly inexpensive , toolstation and the like should sell them. Make sure you wear goggles / mask as no matter where you think is best to stand, it will get you in the face somehow 😉
Use a drill bit 2mm larger than your stud to make the hole. And if they dont have a bevell cut on the end of the stud, try to cut one on with a grinder etc
https://www.toolstation.com/search?q=Hole%20pump
Do a couple of puffs, then use one of these, then couple more, then final clean with brush if you want to be thorough
https://www.toolstation.com/fischer-brush-hole-cleaning-accessory-set/p35801
The resin fixed bolts is what i was think ing of, and you could use a track pump or similar to blow the holes out, unless youve got a compressor, which is a much better idea really. Chuck a rag over tge top if youre using a compressor though, you dont want tbat in your eyes.
TBH a good quality zinc plated bolt does give decent proteciton, when it's in good condition. But tool marks from installing it can be enough to seriously knacker that, as can knocks picked up in manufacture, packaging etc. So it's not so much how good the bolt can be, it's more that by the time it's in situ, it's not that good any more
For the best long term corrosion resistance Hot Dip Galavised bolting is the only way to go (other than 304/316 stainless). Bear in mind that special HDG nuts are required too. These have the threads appropriately oversize to compensate for the Zinc thickness.
You don't see Zinc Plated (BZP/Passivated etc.) fasteners on motorway armco barriers or on any steel stuctural work.
or on any steel stuctural work.
If its Galvanised steel then its galvanised bolts.
Painted steel then its BZP all day long
Painted steel then its BZP all day long
Hopefully they last longer than a day 😂
A2 stainless fixings plus chemfix. The rawlplug blue one is the most popular.
Key thing is getting the dust out. M10 should be plenty big enough with a 12 or 14mm drill
SDS is your friend and you may need a Rebar cutter if your concrete is structural.
Washer to spread the load and a dry day
Some chemfix resins are styrene free iirc this is for indoor use as its less smelly, you don't t need this type