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Galvanized vs. Stainless for embedding in concrete
March 11, 2008
Q. As a contractor, we are replacing rusted parking lot light poles for our customers all of the time. The concrete bases are structurally sturdy and there is no need to replace these. However the base of the steel poles AND the anchors rust and cause the poles to fall over.
We have a process where we grind off the anchor bolts, drill new holes in the existing concrete base and use a structural grade epoxy (Hilti HY150max) to secure the new anchor bolts to mount the pole too.
My question has to do with the type of anchor bolts we should use. All of the pole manufactures ship us Galvanized anchor bolts. However, I hear many say that stainless steel anchor bolts & nuts will last longer, especially in areas that use reclaimed water in the landscaping sprinklers or the base of the pole is below grade and exposed to wet soil all the time.
The other problem is that if you suggest stainless steel, getting a bolt 1" in diameter by 30" long in the grade you recommend is not easy to find.
1) What is the most readily available corrosion resistant material in a situation like this, galvanized or stainless steel anchor bolts & if stainless, how much better than galvanized and what grade?
2) Is there something else that I should consider, aluminum, titanium, etc that would work just as well or better?
Thanks for your consideration.
Specifier / Contractor - Santa Ana, California
Q. We plan to embed some pipe sections in-ground (in concrete) to serve as sockets for an easily erected, occasional use shade structure (which may comprise some form of tubing etc., supporting shade cloth or lattice panels). Which metal pipe will corrode the slowest: aluminum, stainless, or plain steel?
Al Cellhomeowner - Rancho Palos Verdes
March 12, 2008
A. If it is totally surrounded by concrete, Look at schedule 80 or even better schedule 120 PVC pipe. It is available on line from a few businesses. NO corrosion.
James Watts- Navarre, Florida
March 14, 2008
A. Clearly stainless is more corrosion resistant than aluminum, steel, or even galvanized steel. The issue with stainless anchor bolts is that you need the right grade of stainless to have the tensile strength required. Have the bolts you need fabricated in any machine shop out of 400 series stainless. 300 series is not strong enough for this application. The bolts will cost twice what galvanized cost but you will never see them rust off.
Ron Cooley- Hillsborough, North Carolina
March 16, 2008
September 23, 2009
A. Ultimately for corrosion resistance use 316 stainless steel anchors and stainless steel light poles :-). If corrosion at the base/bolt interface is happening you may suggest replacing steel light pole base with the correctly calculated 316 ss base plate and weld it to the pole. Not sure about light poles but we have processed steel/stainless combinations.
Electropolishing the 316 will be the ultimate for corrosion resistance.
You will need to recalculate the size due to lower 316 stainless tensile strength.
Hilti sells HIT-RTZ Anchor Rod or you can use the correct sized 316 stainless threaded rod readily available.
If you use stainless anchors and the light pole base plates are mild steel or galvanized steel there will be contamination corrosion where the mild steel/stainless touches. To a lesser degree, the stainless will corrode slower and keep its structural integrity longer than steel.
Another no-no, with concrete involved, do not clean the concrete with muriatic acid. This will compromise the passive layer of 304/316 stainless steels.
My suggestion of the 316 s/s Hilti HIT-RTZ anchors is based on an EP job. Floating concrete dock fastened together with electropolished
316s/s Hilti HIT-RTZ anchors, 316 chain, washers, Nylock nuts, etc. Located in a marine salt water environment the stainless has yet to fail at any interface.
electropolishing shop - North Vancouver, British Columbia, Canada
Hi. When speaking of galvanizing, please remember that hot dipped galvanizing is much heavier and more corrosion resistant than "electrogalvanizing" (zinc electroplating); don't let sellers don't try to obfuscate things by letting them call zinc plating "galvanizing". Galvanizing is a premium finish for re-bar and should work well for anything embedded in concrete.
As for stainless, again stainless steel is now very widely used for embedded rebar, and rebar suppliers should be able to advise on the relative advantages of type 316, vs. nitrogen hardened, vs. duplex, etc. if you can't quickly learn enough just by googling "stainless rebar". Good luck.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
July 2012
Q. Dear Forum members,
I have a requirement wherein we need to embed a steel Pipe with Puddle flange in concrete wall (water retaining structure wall).
We were suggested to use SS , but I have doubt over this as the SS is prone to chloride attack.
Kindly suggest what material or Grade of SS shall be suitable for this.
Regards,
Deepankar
- GURGAON, Haryana, INDIA
July 26, 2012
A. Hi Deepankar. As you see, we appended your inquiry to a thread which may answer it for you.
I'd suggest contacting a supplier of galvanized and stainless rebar, who will have a great deal of experience and history in this subject.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
July 26, 2012
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