# Can Zinc/Aluminum coated anchor rods be used in concrete?

Bolts and anchor rods that are very high strength ($F_u$ > 150ksi) are not supposed to be galvanized. This is because of concerns about hydrogen embrittlement. This includes ASTM A 490 bolts and ASTM A 354 Gr. BD anchor rods.

The project in question has very high lateral loads and is outdoors. Typical ASTM F 1554 Gr. 105 anchor rods end up being very large in diameter. This is why ASTM A 354 Gr. BD rods (2.5 inch diameter) are specified. There is no space for more anchor rods.

Since the project is outdoors, a corrosion protection coating is required. The only coatings that can be used are Zinc/Aluminum coatings such as ASTM F 1136 Grade 3.

There is a history of aluminum not being used in contact with concrete because of corrosion concerns. This seems to be specifically with solid aluminum.

Do I need to be concerned with the aluminum content of this coating reacting with the concrete that the anchor rods are embedded in?

• Page 7 of this document - cement.org/docs/default-source/th-buildings-structures-pdfs/… - addresses corrosion of nonferrous metals embedded in concrete, and some strategies to mitigate risk. I'm also not sure that aluminum coating have lower embrittlement risks - doesn't the steel still need to get pickled? Could you consider using uncoated steel anchor bolts and protecting the exposed portion with a zinc rich paint or epoxy or do contract documents preclude that? – Ethan48 Feb 14 '15 at 16:52
• @Ethan48 Pickling is an issue, so it needs to specifically not be done. The issue with only painting the exposed part of the anchor rod is that most anchor rods are coated full depth or at least ~12in below the concrete surface. This is done to keep water from infiltrating down along the rod and causing corrosion. – hazzey Feb 14 '15 at 20:27
• If you are worried about corrosion (e.g. underwater, etc.), then I think utilizing a sacrificial anode would probably be the best solution. I'm not sure if you can find a reliable way to completely stop corrosion, so it would be more reliable to just leverage the electrochemical potentials from sacrificial components. I thought hydrogen embrittlement on hdg items comes into play during welding or when applying high heat? – agent provocateur Apr 20 '16 at 22:00