I'm making a couple of steel anchors that will be encased in concrete, they are for bolting a 2 post lift to. Anyway is it worth coating them in anything before they are set into the holes and the concrete poured in?
Rebar isn't coated because it relies on the concrete cover for corrosion resistance, typically a minimum of 50mm. If you're fixing anchors into concrete you would do well to have some corrosion resistance to prevent them rusting through at the top of the hole, especially for something like a car ramp. Most concrete anchors are zinc plated to provide corrosion protection.
Resin anchors are a good option. This year I was lifting some 5 tonne sections of concrete off the edge of a building about 100metres up over the public footpath. Very high risk work so we did extensive load testing on the anchors. Using 16mm 8.8 threaded rod fixed into a 200mm deep 18mm hole with Hilti HIT HY200 resin, we tested to 30kn (twice the expected load) and every one of them passed. I got the guy to pull one until it failed. He got to 90kn (approx. 9 tonnes) and it still held in the anchor but it did pull the nut half way through the heavy washer.
Interesting stuff Pete, basically I'm making a plate the same size and shape as the base of each post which will be 500mm below the surface, with 5 30mm diameter steel bars extending up to finished floor level in the same bolt hole pattern as the base of the post's. These will be drilled and tapped M18 and the lift will be bolted to these once the concrete has been in for a few weeks.
It's a good plan. Typically, they would fix the fasteners to the anchor plate with a nut top and bottom. Use paper cones to allow the bolts to bend then grout them upafter installation OR fix a plywood template just above floor level, again bolted top and bottom. Tape the threads up to avoid getting wet concrete on them and save yourself a headache. I'd build the ramp after 7 days, maybe 14 if you want to be sure - you ain't pulling that plate through cured concrete even if you don't wait the full 28.
Epoxy is typically used for coating rebar in areas of high salinity and aggressive ground conditions. I’ve done a bit of work in the middle east where all the rebar had to be coated but never needed it in the UK. Even in coastal/marine areas I doubt you’d find rebar/anchors Coated.
Steel fixings that are in the concrete are fine. Fixings that are exposed to air - also fine. The bit that will cause trouble is where the bolt/stud/whatever comes out of the floor and passes through the base plate. You get the floor wet and because of the tiny gap the water just rests there and eats through the bolt. I can't tell you the number of steel columns I've pulled over with a demo robot where the bolts or rebar starter bars just snapped where they had rusted half way through, in the case of rebar it's where the kicker is formed then the column is cast on top of it with a poor day-joint so wicks in and does it's work.
Long story short either use plated fixings or paint the bolt for a few inches at floor level before you pour the concrete.