×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Anchor Bolts for Aluminum

Anchor Bolts for Aluminum

Anchor Bolts for Aluminum

(OP)
I've got a project where Aluminum columns (and base plates) are being anchored to a concrete pier/footing. The contractor used your everyday common steel threaded anchor rods. In less than two weeks they are completely rusted over. The contract documents called for hot-dipped galvanized anchor bolts. (before judging, we did not provide the design or specifications, simply consulting on a separate portion of the larger project)

I'm thinking of having the contractor cut off and drill-in epoxy grout anchors.

Will the galvanized anchor bolts react to the aluminum? Should I use aluminum anchor bolts? If alum, what affect would the anchors have in steel reinforced concrete?

Thank you,

MLM

RE: Anchor Bolts for Aluminum

Galvanized steel anchor bolts should be OK with aluminum.
As an extra precaution the contact areas could be painted with insulating paint.

http://www.welding-advisers.com/

RE: Anchor Bolts for Aluminum

Al bolts are unlikely to be strong enough if they were not specifically incorporated into the design.  Zinc is the most compatible coating for steel bolts that is also relatively cost effective.

RE: Anchor Bolts for Aluminum

Aluminum and Zinc are really close together on my Galvanic Corrosion Potential Chart.

RE: Anchor Bolts for Aluminum

(OP)
Is that good thing or a bad thing?

MLM

RE: Anchor Bolts for Aluminum

Its a good thing... the farther apart two metals are on the galvanic series the greater potential between them, hence more aggressive attack.

Aluminum embedded in and in direct contact with concrete is not acceptable.  A chemical reaction occurs and the concrete literally self destructs from the expansion (product of the reaction, just like rust on carbon steel that is allowed to corrode in concrete).  I don't know about epoxy grouted aluminum in concrete but I've seen slabs with aluminum cast into it break themselves apart.

RE: Anchor Bolts for Aluminum

I have a question to go along with this.  I have noticed in the past with aluminum panels that the manufacturer of the panels has recommended stainless steel screws with some kind of special washer between the steel and the aluminum.  Does that line of thinking work also in this case, say with using stainless steel anchor bolts or epoxy bolts with an aluminum base plate?

RE: Anchor Bolts for Aluminum

(OP)
How good is stainless in direct contact with Aluminum? When this issue first came up, the only thing that I thought of was stainless. Then came the comments about the specs calling for hot-dipped galvanized. I've always assumed that stainless was preferred, if not required. Is that assumption correct?

MLM

Also, thanks for the input.

RE: Anchor Bolts for Aluminum

ASTM A-153 or ISO 1461 covers hot-dip galvanizing.  I think it's more of a cost factor when considering Stainless verses galvanized steel.

RE: Anchor Bolts for Aluminum

Stainless should not be in contact with aluminum. Stainless fasteners should be Cadmium or Zinc plated before
being inserted in aluminum bodies. Usual anodizing or conversion coating are not protective enough at the contact place.

http://www.welding-advisers.com/

RE: Anchor Bolts for Aluminum

In my experience (27 years in the petrochemical industry), aluminum and stainless fasteners are acceptable in most environments.  Althought they are far apart on the galvanic scale, the typically much larger area of the aluminum part compared to the fastener reduces to nearly nil the tendency of the aluminum to corrode.  However, in this case, I'd definitly use galvanized anchors - they were specified, are compatible, are probably more available not to mention less costly.  Note that the environment is a critical issue - If this is on the seashore, or exposed to wet atmosphere, or under water, or vibrating from machinery, etc then corrosion needs to be re-evaluated.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources