Stainless steel poles

[traffic light guy]

I've noticed that certain areas in District 6, such as Lower Merion, use stainless steel poles in order to mount their signals. This makes it extremely difficult to tell how old the signals are, some of these installs include Eagle heads that are over 40 years old. Are these poles original, I get that these poles are stainless steel, but so can other things be called "stainless steel", like faucets and flagpoles, and they rust up. How come these poles have been up for several decades, and don't have a single stain. It wouldn't make sense to re-install old signals onto new poles, since this entire area has these. Some of these have PennDOT's arched pole design, which was discontinued around 1977.

Here are several setups that include signal heads that are over 40 years old:

https://www.google.com/maps/@40.0159079,-75.2632803,3a,75y,184.08h,105.28t/data=!3m6!1e1!3m4!1s71QDGGDHuDm3SecLwnAOFA!2e0!7i13312!8i6656?hl=en

https://www.google.com/maps/@40.0162606,-75.3207543,3a,75y,51.01h,103.04t/data=!3m7!1e1!3m5!1sd8TQMbVXTAIQlj5syQGKKQ!2e0!5s20170901T000000!7i13312!8i6656

[kalvado]

There are different grades of stainless steel, and better grades are - guess what? - cost more to much more. For example common cheap food grade is scratch-prone 18-0 which is often seen in lower grade restaurants with heavily beaten flatware; 18-10 aka AISI 304 holds better, and AISI 316 with added tungsten and molly can withstand seawater for extended periods of time.
Maybe there is a reason why DOT chosen to use a more expensive material in certain area, maybe it is local climate which is more forgiving to materials. Or maybe just better coating (I cannot really tell if these are actually stainless, not plated)

[Brandon]

Are you sure those are stainless steel?  The silver-colored poles that never rust are typically made of aluminum.

Examples (that are just as old):
https://goo.gl/maps/qM8PJAk9tRL2
https://goo.gl/maps/YqNzMz7zK8p
https://goo.gl/maps/ViYykknhKQx

Each of those examples is a 35-40 year old aluminum truss.

[traffic light guy]

Are you sure those are stainless steel?  The silver-colored poles that never rust are typically made of aluminum.

Examples (that are just as old):
https://goo.gl/maps/qM8PJAk9tRL2
https://goo.gl/maps/YqNzMz7zK8p
https://goo.gl/maps/ViYykknhKQx

Each of those examples is a 35-40 year old aluminum truss.

They are, several signal geeks that live within my area have reffered to Lower Merion's poles as stainless steel

[kalvado]

Are you sure those are stainless steel?  The silver-colored poles that never rust are typically made of aluminum.

Examples (that are just as old):
https://goo.gl/maps/qM8PJAk9tRL2
https://goo.gl/maps/YqNzMz7zK8p
https://goo.gl/maps/ViYykknhKQx

Each of those examples is a 35-40 year old aluminum truss.

They are, several signal geeks that live within my area have reffered to Lower Merion's poles as stainless steel

Can you  do a quick magnet test on those?

[Pink Jazz]

Are you sure those are stainless steel?  The silver-colored poles that never rust are typically made of aluminum.

Examples (that are just as old):
https://goo.gl/maps/qM8PJAk9tRL2
https://goo.gl/maps/YqNzMz7zK8p
https://goo.gl/maps/ViYykknhKQx

Each of those examples is a 35-40 year old aluminum truss.

They are, several signal geeks that live within my area have reffered to Lower Merion's poles as stainless steel

Can you  do a quick magnet test on those?

Not all grades of stainless steel are magnetic.  Grades that are magnetic are the 400-series of stainless steel, which include ferritic and martensitic varieties.  300-series or austenitic stainless steel is non-magnetic.

[jakeroot]

Are you sure those are stainless steel?  The silver-colored poles that never rust are typically made of aluminum.

Examples (that are just as old):
https://goo.gl/maps/qM8PJAk9tRL2
https://goo.gl/maps/YqNzMz7zK8p
https://goo.gl/maps/ViYykknhKQx

Each of those examples is a 35-40 year old aluminum truss.

They are, several signal geeks that live within my area have reffered to Lower Merion's poles as stainless steel

Can you  do a quick magnet test on those?

Not all grades of stainless steel are magnetic.  Grades that are magnetic are the 400-series of stainless steel, which include ferritic and martensitic varieties.  300-series or austenitic stainless steel is non-magnetic.

[traffic light guy]

Are you sure those are stainless steel?  The silver-colored poles that never rust are typically made of aluminum.

Examples (that are just as old):
https://goo.gl/maps/qM8PJAk9tRL2
https://goo.gl/maps/YqNzMz7zK8p
https://goo.gl/maps/ViYykknhKQx

Each of those examples is a 35-40 year old aluminum truss.

They are, several signal geeks that live within my area have reffered to Lower Merion's poles as stainless steel

Can you  do a quick magnet test on those?

Not all grades of stainless steel are magnetic.  Grades that are magnetic are the 400-series of stainless steel, which include ferritic and martensitic varieties.  300-series or austenitic stainless steel is non-magnetic.

No clue, I've also heard Ian simply refer to them as silver

[roadman65]

Isn't New Jersey's truss style mast arms on aluminum? I know they are very hollow and make a sound when you bang it.  Plus, they are on breakaway bottoms unlike the monotube mast arm poles which have a wider diameter pole where the older truss arms had a pole similar to the light poles.

[kalvado]

Are you sure those are stainless steel?  The silver-colored poles that never rust are typically made of aluminum.

Examples (that are just as old):
https://goo.gl/maps/qM8PJAk9tRL2
https://goo.gl/maps/YqNzMz7zK8p
https://goo.gl/maps/ViYykknhKQx

Each of those examples is a 35-40 year old aluminum truss.

They are, several signal geeks that live within my area have reffered to Lower Merion's poles as stainless steel

Can you  do a quick magnet test on those?

Not all grades of stainless steel are magnetic.  Grades that are magnetic are the 400-series of stainless steel, which include ferritic and martensitic varieties.  300-series or austenitic stainless steel is non-magnetic.

I don't expect to find 316 in those poles anyway. 18-0 is a reasonable bet - as well as zinc plated stuff