In March of this year (2021) a resident sent me a picture of our steel handrails in the Dot, and the picture showed copious surface rust. To say I was horrified is an understatement, as these handrails had been installed last fall and have only seen a light winter's worth of use.
I immediately sent it to our city manager, who referred it to our construction manager and architect for review.
From there, a recommendation was made to clean the stainless steel. Excerpt from an email:
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"It’s only been a few months since they were installed, but the conditions that damage stainless steel (salt, moisture, de-icing agents) are typically higher in the winter than others. The stainless steel will be “polished” in-house, but comprehensive cleaning on the rails and bollards should be done by a specialist. Stainless steel needs to be maintained annually, especially when it’s exposed to the elements. It should be called stain-“less” steel because it will still accumulate surface rust and grime when exposed to water and de-icing agents. The handrails and bollards are exposed to moisture and de-icing chemicals throughout the winter. Additionally, when guests touch the handrails, dirt and oils can transfer from their hands onto the rail. When the stairs aren’t used, salt and moisture can stay on surfaces for even longer. Even when a building is used less, the rails still need maintenance. Most sources suggest a comprehensive annual cleaning for our geographical location, in addition to daily and quarterly maintenance. Bruce Campbell said that this maintenance schedule in line with other parking structures. Reef has been cleaning the stainless steel daily, and DPW has been cleaning it quarterly. The doors and elevators will be cleaned annually by DPW as well. Since they have less exposure to the elements, and therefore, less surface rust and corrosion, they do not require cleaning by a stainless steel company. Excessive pitting and permanent damage over the next couple of years could likely be an issue with materials and/or craftsmanship, so it is something the City will have to monitor. Both contractors that quoted didn’t seem to think the damage was excessive. Failing to maintain the stainless steel would likely make any potential warranty claims much more difficult because the contractor could argue that a lack of maintenance was the cause of the deficiency."
The architect from the Dot project also weighed in:
"The stainless steel handrails were always 316 and were not part of the guardrail re-design/VE. There is a test that can be done to verify whether or not 304 or 316 was installed. If there is excessive surface rust re-appearing we might want to get that test done. TEC could do it for us. It wouldn’t have been a test that specifically called for because it’s just about honesty not structural performance. Typically, once the construction stops and the steel gets cleaned real good and the oil from people’s hands on the handrail ‘treats’ the steel the surface rust seems to become more manageable or under control. There is always the coating that can be used but I think that’s a ‘forever’ undertaking. Cleaning the handrails between twice a year and once a quarter would not be unreasonable. The Ann Arbor DDA has some decent techniques for keeping their stainless clean. You could contact Ed Wheeler and he could offer some advice. Daniel P. Mooney, AIA Principal Edge Design Associates 24 Frank Lloyd Wright Dr. Suite H1800 PO Box 533 Ann Arbor, MI 48106"
This is where it helps to have an engineer in the household and a friend in the metals industry, because even though this is a low-cost maintenance item (~7k), the reason marine grade stainless steel is used in outdoor applications is due to the ability it has to resist rusting.
Should stainless steel rust?
In short, no, not if it's grade 316 stainless steel under normal conditions.
Iron is the largest component of stainless steel, but everyone knows that it only takes water or damp air to make iron rust and break down. That's why stainless steel alloys iron with other metals, making a mixture that creates a stronger, more rust-proof metal. There are different grades and mixtures, with differing degrees of corrosion resistance. The two most common grades are 304 and 316.
Differences between stainless steel grade 304 vs 316
The non-sciencey answer is that the main difference between 304 and 316 steel is that 316 more resistant to corrosion from salt.
The sciency difference between the grades of steel is the presence of molybdenum in stainless 316. Molybdenum is a chemical element used for the strengthening and hardening of steel. Its main function in stainless 316 is to help fight off corrosion from chlorides (salts).
Grade 316 steel is considering marine grade steel. It is used on boats, on bollards and rails near the coast and salty pathways, etc. A great example you can see locally is the steel guardrail down by the Detroit river along the riverwalk.
We supposedly have 316 steel on our handrails, but given the rust, I am skeptical. It's possible that it is 316 and that somehow the passivation layer was wrecked. A passivation layer (non-reactive layer) is really thin, and can be damaged by abrasion, expansion/contraction, or chemicals.
It is also possible that we have 304 steel. Grade 304 steel easily corrodes in the same way we see in the original picture. This article was sent to me by a materials engineer after our council meeting https://www.imoa.info/molybdenum-uses/molybdenum-grade-stainless-steels/architecture/deicing-salt-handrail-article.php?fbclid=IwAR08M9FWrwQH5nLCKLGFfVO7RoomnENjOiwB38A0wiUV7djw9mSR3kPZroI
Picture excerpt:
Compare the pictures in the article above to the pictures I took of the handrails the morning of our meeting for the approval of the handrail cleaning, seen below.
Next Steps
I voted to approve the cleaning of the steel handrails so we wouldn't be in breach of any warranty obligations. We have a 1 year warranty on these handrails, so I urged us to get a quote for failure testing of the steel. As a first step our DPW facilities manager recommended that we do an in-place test of the material to determine if it is 304 vs 316, and assess from there. The cost to do this is $3500, which we approved June 28th on this agenda item: https://d2kbkoa27fdvtw.cloudfront.net/ferndalemi/974ffb86408e7bd25efee974c52371ca0.pdf
I would have preferred to go straight into a failure test, but since that would involve taking a small piece of the rail out to send out for testing, field testing was preferred.
You can listen to my questions from the first meeting concerning cleaning the rails here: https://ferndalemi.granicus.com/player/clip/821
Special thanks to the resident that raised the red flag, and the resident who works in the steel industry who contacted me after our meeting to say that 316 should not rust the way those handrails were rusting.
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