galvanized steel and concrete

[1.8T]

Couple of quick questions as i need to fabricate and install some galvanized posts for someone, does concrete eat away at galvanized steel? and will using stainless steel fixings on galvanized steel cause a reaction to either the galvanize or stainless, thanks

 

[Terrapin]

No problem with galvanised steel & concrete - indeed galvanised rebar is used where there is a high risk of corrosion to standard rebar. SS & Galv is also not really a problem unless you are using it in an area where there will be high salt contact - e.g. marine/boats/by sea etc.

 

[1.8T]

Good stuff, one final question i forgot to ask earlier was regarding tapped holes, my intention was to drill and tap all holes prior to galvanizing then run a tap through them afterwards to clean them hopefully without exposing the steel, smallest threads would be m6 are the smaller theads likely to be melted during the galvanizing process beyond being usable, the small threads are for ornamental capping pieces to prevent them being pinched (they need to be removable) and wont be taking any load at all

 

[MattF]

I've always found a coating of Copper(slip|ease) etc. helps with regards to preventing corrosion on exposed metal. I'd just lather that on the retapped holes and bolts, personally.

 

[Hitch]

For m6, I'd drill and tap them after galving.
It's a bit of a waste of time tapping prior to galvanising. Just put a near size drill through, then redrill and tap after.

 

[Welderpaul]

If the steelwork is galvanised, i would use galvanised fixings rather than stainless. It affords the fixings the same protection as the steel so why spend more money on them (Around twice the cost).

 

[1.8T]

The reason i wanted to drill and tap before hand was i wanted to avoid breaking any of the galvanized coating, yes i know im being fussy but assuming the threads dont get melted during the galvernizing process its only a couple of minutes to clean them out with a tap, paul i already have the stainless fixings so not an issue, not sure i could even buy m6 galvernized bolts locally

 

[Hitch]

Youll break the galv when you retap it anyway.....

They will probably fill up completely and will need drilling out after anyway.

 

[feen]

I had m6 threaded holes on a trailer I recently finished. Most of the holes filled up completely and when re-drilled the new hole wasn't exactly centred on the old hole. By the time I re-tapped them after galv they were oversized and stripped easily. After that the rest went in with loctite and just tight.

If I was doing it again, I'd drill a 5mm hole before galv and leave it at that.

I'm no expert though.

JF

 

[Flathead_Dave]

Rustoleum do a cold zinc spray can for recoating galv after repair work.
I'd drill and tap after coating,spray the above in the holes,and fit the screws while it was still wet.