Compatible metals question.

[Pixels Are Bad Mmmkay?]

We are producing an outdoor blade sign that will hang from an aluminum hanger that is manufactured by an outside company. The hanger is made from powder coat painted aluminum and we will be using quick links, chain, and eye hooks to mount the sign to the hanger. To mount the hanger to the wall, the manufacturer calls for 3/8" fasteners. The hanger is being applied to a brick and mortar wall that is approximately 12" thick. The owner, who's father is a contractor, will be installing this with his father's help and they plan to drill clean through the wall in 5 places and bolt the hanger through the wall.

My question is, what would be the best hardware to couple with the painted aluminum. I was thinking stainless steel would be ideal, but is there something essentially less costly that would work well without any sort of strange corrosion happening? Am I over-thinking this? Any guidance is much appreciated.

 

[Billct2]

I'd use galvanized bolts, but stainless is nice if they have the money.
Thru bolting is sturdy as hell but if they really want solid thay can add a plate on the inside too.

 

[Pixels Are Bad Mmmkay?]

I thought galvanized and aluminum are a bad combination or should it not matter since the aluminum is powder coated? Again, perhaps I'm over-thinking this. I just want to be sure this thing won't corrode and fall apart in 5-10 years. I also want to be sure that it won't do anything funky like leave a trail of rust down the brick wall or the sign face.

 

[jfiscus]

On ambulances and such where stainless and aluminum would otherwise come in contact most manufacturers use isolaters in-between/around the fasteners. (like nylon sleeves)

 

[Billct2]

Since the aluminum is powder coated it should be fine. But if you're concerned a nonmetallic washer could be used.

 

[Gino]

User a teflon washer or collar and you should be fine. Also, the plate on the inside is a really good idea. When using all thread for installations like this, we almost always try to use a backer plate on the inside. Also, if they need this kind of support, are you using guy wires ??

 

[Pixels Are Bad Mmmkay?]

User a teflon washer or collar and you should be fine. Also, the plate on the inside is a really good idea. When using all thread for installations like this, we almost always try to use a backer plate on the inside. Also, if they need this kind of support, are you using guy wires ??

They are not using guy wires. The hanger is engineered to hold a sign up to 16 sq. ft. and 56 lbs. We are building a sign that is 9 sq. ft. and weighs in at approximately 23 lbs. so we are well within the engineer's guidelines. I didn't suggest going all the way through the wall. I was actually surprised when the customer said it is their intention to do so.

 

[Gino]

They are not using guy wires. The hanger is engineered to hold a sign up to 16 sq. ft. and 56 lbs. We are building a sign that is 9 sq. ft. and weighs in at approximately 23 lbs. so we are well within the engineer's guidelines. I didn't suggest going all the way through the wall. I was actually surprised when the customer said it is their intention to do so.

Yeah, I agree. I thought when you said five all threads, I figured a sign about 4' x 5' and about 75 to 100lbs. Once ya get much past 25lbs, it's still a good idea to use them to prevent back & forth swaying which puts a lot of strain and stress on even five lags, but all-thread, probably not too much.

 

[tadisch treehouse]

cut cost on hardware not a good idea, use stainless now and save yourself the lawsuit later. Powder coat is a finish that can not take any wear and will corrode easily, protect yourself from any liability issues as with anything hanging overhead it can fall down, wind will be the biggest threat to sign hangers.

 

[AF]

http://engineersedge.com/galvanic_capatability.htm

 

[Pixels Are Bad Mmmkay?]

cut cost on hardware not a good idea, use stainless now and save yourself the lawsuit later. Powder coat is a finish that can not take any wear and will corrode easily, protect yourself from any liability issues as with anything hanging overhead it can fall down, wind will be the biggest threat to sign hangers.

The point isn't to find a cheaper solution, but to find the appropriate fasteners to combine with aluminum as to avoid galvanic corrosion of the dissimilar metals...

My question is, what would be the best hardware to couple with the painted aluminum. I was thinking stainless steel would be ideal, but is there something essentially less costly that would work well without any sort of strange corrosion happening?

By essentially less costly, I'm saying that stainless steel is the most costly fastener material that is readily available. However, as I'm finding out, it is not the best material for this situation...not even close. Since researching this more, I've found that stainless steel is not recommended for use with aluminum as the aluminum, being the less noble metal will corrode. My best option would in fact be aluminum fasteners, but I'd likely be hard pressed to find aluminum quick links, eye hooks, chain, and bolts. They could use aluminum threaded rod, but the common 6061 T6 aluminum rod that I've found is a medium tensile strength grade, hence I personally would not trust it, albeit that is arguable.

As has been stated, and I'm starting to agree, Galvanized fasteners, which it just so happens are much less costly, would be ideal in this situation as they have less anodic potential. These, in combination with teflon washers sounds like a good situation.

 

[Pixels Are Bad Mmmkay?]

http://engineersedge.com/galvanic_capatability.htm

Thank you, sir.

 

[Pixels Are Bad Mmmkay?]

https://www.youtube.com/watch?v=0ONe-Qfdi0c