Stainless Straps in the Water

[Nermal]

It does seem strange. I have a 304 bracelet (not watchband) which I've worn pretty much 24/7 for about seven years and it's showing no signs whatsoever of rust or anything. As noted above, 316 is even "better" in water so I can't imagine any technical reason to say not to get it wet.

I think one of the earlier posts may be on the right track; Apple wants you to also buy a sport band.

 

[44267547]

It does seem strange. I have a 304 bracelet (not watchband) which I've worn pretty much 24/7 for about seven years and it's showing no signs whatsoever of rust or anything. As noted above, 316 is even "better" in water so I can't imagine any technical reason to say not to get it wet.

I think one of the earlier posts may be on the right track; Apple wants you to also buy a sport band.

I would say most who purchase the Apple Watch, start with a model that comes with a sports band. And if they decide to upgrade to the stainless link, that usually ends up a separate purchase with the price point. I own the regular and black stainless link 316 L, they hold up really well. I have zero issues with them after two years of ownership with water corrosion.

 

[MartyCan]

As for the cost of the band, I bought a link bracelet off Amazon. Just got it tonight and I'm really happy for not spending almost $400 more for Apple's version. I may hit Apple's store and compare them.

I bought a "space black" link bracelt off Amazon last year. I am not complaining but I did get what I paid for. It's not as nice as Apple's and the finish is coming off of it. For what I paid it's not a big deal. Probably would not buy again.

 

[Thai]

Stainless steel comes in various compounds.
316L would be resistant to rust.
However it's expensive. Most likely they used a cheaper grade. Try attaching a magnet to it. The more it attracts, the more iron (and potential corrosion) in your strap.

Apple uses 316L.

 

[OriginalAppleGuy]

I bought a "space black" link bracelt off Amazon last year. I am not complaining but I did get what I paid for. It's not as nice as Apple's and the finish is coming off of it. For what I paid it's not a big deal. Probably would not buy again.

The colored bands add a level of complexity that will probably lead to a failure of some kind. It's one of the reasons I prefer not to have "plated" products. I paid about $70 for the SS link bracelet. Being the natural color of stainless steel, I'd hope I wouldn't have any issues with finishes coming off. Besides, for that price, I can buy many of them before getting to what Apple charges for the same thing ($450 - ouch!).

 

[MartyCan]

The colored bands add a level of complexity that will probably lead to a failure of some kind. It's one of the reasons I prefer not to have "plated" products. I paid about $70 for the SS link bracelet. Being the natural color of stainless steel, I'd hope I wouldn't have any issues with finishes coming off. Besides, for that price, I can buy many of them before getting to what Apple charges for the same thing ($450 - ouch!).

Same logic I used and I am certainly not arguing. Still the one I got on Amazon was not as nice or "tight" as the Apple version seems to be. I still use it so again you will probably be quite happy with it unless you have high OCD tendencies

 

[44267547]

The colored bands add a level of complexity that will probably lead to a failure of some kind. It's one of the reasons I prefer not to have "plated" products. I paid about $70 for the SS link bracelet. Being the natural color of stainless steel, I'd hope I wouldn't have any issues with finishes coming off. Besides, for that price, I can buy many of them before getting to what Apple charges for the same thing ($450 - ouch!).

There are similar link bands that are on the market when compared to Apple's OEM band. But in terms of the actual comparison, there is no match compared to Apple's OEM link band.

Apples stainless steel link OEM band is expensive, but the ingenuity and craftsmanship is on a completely different level from any third-party stainless steel watch link band. And I do Own both the black and regular stainless steel link bands for comparison.

 

[Ixidor]

316L stainless steel is non-magnetic, so I don't think the Milanese loop is made from it. All other stainless steel components used in the Apple Watch (case, link bracelet etc) are made of 316L.

Basically, the 300 class of stainless steels are known as austenitic steels and they are not magnetic. Most other grades are martensitic or ferritic, and these will be magnetic.

Anyway, I don't see the milanese loop advertised as 316, because if it is, then it's false advertising (I'm a materials engineer specialising in stainless steel research). While it is possible that some austenitic steels may have some residual magnetism due to a small amount of iron that remains ferritic/martensitic, as far as I know, the milanese loop is highly magnetic.

Also, just because a stainless steel is marine grade doesn't mean it cannot corrode. The most likely form of corrosion I can think of, is known as crevice corrosion (wiki has a good article on this), where water or sweat stuck within the links, mesh, adapter etc accelerates corrosion. And if it does corrode, it'll most probably form tiny holes (i.e. pitting corrosion) as opposed to forming a layer of "rust". I doubt this will be an issue in real life, but I'm guessing that's why Apple doesn't recommend its use.

Side note: magnetism has nothing to do with the "amount of iron" in the alloy. Austenitic stainless steels like the 316L is simply not magnetic because of the way the iron atoms are arranged.

 

[Thai]

316L stainless steel is non-magnetic, so I don't think the Milanese loop is made from it. All other stainless steel components used in the Apple Watch (case, link bracelet etc) are made of 316L.

Basically, the 300 class of stainless steels are known as austenitic steels and they are not magnetic. Most other grades are martensitic or ferritic, and these will be magnetic.

Anyway, I don't see the milanese loop advertised as 316, because if it is, then it's false advertising (I'm a materials engineer specialising in stainless steel research). While it is possible that some austenitic steels may have some residual magnetism due to a small amount of iron that remains ferritic/martensitic, as far as I know, the milanese loop is highly magnetic.

Also, just because a stainless steel is marine grade doesn't mean it cannot corrode. The most likely form of corrosion I can think of, is known as crevice corrosion (wiki has a good article on this), where water or sweat stuck within the links, mesh, adapter etc accelerates corrosion. And if it does corrode, it'll most probably form tiny holes (i.e. pitting corrosion) as opposed to forming a layer of "rust". I doubt this will be an issue in real life, but I'm guessing that's why Apple doesn't recommend its use.

Side note: magnetism has nothing to do with the "amount of iron" in the alloy. Austenitic stainless steels like the 316L is simply not magnetic because of the way the iron atoms are arranged.

Milanese Loop is 316L metal...clearly written on its box.

 

[Thai]

 

[MartyCan]

You know, the way it's written the 316L SS Magnetic Closure could be taken as a description or the closure only. Not saying it is or isn't but the slightly different font could be telling.

 

[OriginalAppleGuy]

You know, the way it's written the 316L SS Magnetic Closure could be taken as a description or the closure only. Not saying it is or isn't but the slightly different font could be telling.

The only problem is in how the band functions. The entire band has to be magnetic for the "closure" to work.

 

[OriginalAppleGuy]

@Ixidor seems to know what he's talking about. Everything I've found searching the web is 316L doesn't have high magnetism. I see it's listed on the box @Thai shows in the picture but it's strangely missing from Apples website description where other bands have it listed. I wonder if Apple didn't weave in a metal with magnetic properties with the majority being 316L?

 

[Ixidor]

@OriginalAppleGuy

Since Apple did label the box as 316L, I wonder if it was a mistake or if it refers to particular parts of the milanese loop (like how the classic buckle, sports band etc are labeled as 316L stainless steel). However, this is very misleading for the milanese loop because people will expect marine grade corrosion resistance. I can't imagine Apple making a mistake like this though so there must be an explanation.

That being said, 316L can be rendered magnetic if a heat treatment was done to cause it to transform from austenite to ferrite/martensite (for instance, if you cool it to below room temperature). But doing so would cause negative impacts to corrosion resistance, which defeats the purpose of using 316L. Furthermore, Nickel, the element meant to stabilise austenite so the steel is non-magnetic, is quite expensive.

What makes me curious is that the loop is obviously very magnetic.

Anyway, I was just sharing my knowledge on stainless steel metallurgy. I do have the tools to verify the alloy used (part of my job), but I don't have an official loop on hand and even if I do, I'm not even sure if the effort is worth it.

***

Back to the original question. Even if stainless steel straps were made of 316L, I wouldn't recommend getting it wet for extended periods of time. That being said, for 99% of people, this shouldn't be a concern. That said, the potential for pitting/crevice corrosion in stainless steel watches is a well known thing, which is why some higher end watches use other more resistant stainless steels.

All stainless steels though, no matter how corrosion resistant, suffer from this problem. For an expensive watch/strap, best not risk it. But I think that's why Apple advices against using these straps in water. (That said, I'm saying this as a stainless steel engineer. The environments I work with are far more chemically hostile to stainless steels than simply going for a swim).

Just buy a sports band.

 

[44267547]

@OriginalAppleGuy

Since Apple did label the box as 316L, I wonder if it was a mistake or if it refers to particular parts of the milanese loop (like how the classic buckle, sports band etc are labeled as 316L stainless steel). However, this is very misleading for the milanese loop because people will expect marine grade corrosion resistance. I can't imagine Apple making a mistake like this though so there must be an explanation.

That being said, 316L can be rendered magnetic if a heat treatment was done to cause it to transform from austenite to ferrite/martensite (for instance, if you cool it to below room temperature). But doing so would cause negative impacts to corrosion resistance, which defeats the purpose of using 316L. Furthermore, Nickel, the element meant to stabilise austenite so the steel is non-magnetic, is quite expensive.

What makes me curious is that the loop is obviously very magnetic.

Anyway, I was just sharing my knowledge on stainless steel metallurgy. I do have the tools to verify the alloy used (part of my job), but I don't have an official loop on hand and even if I do, I'm not even sure if the effort is worth it.

***

Back to the original question. Even if stainless steel straps were made of 316L, I wouldn't recommend getting it wet for extended periods of time. That being said, for 99% of people, this shouldn't be a concern. That said, the potential for pitting/crevice corrosion in stainless steel watches is a well known thing, which is why some higher end watches use other more resistant stainless steels.

All stainless steels though, no matter how corrosion resistant, suffer from this problem. For an expensive watch/strap, best not risk it. But I think that's why Apple advices against using these straps in water. (That said, I'm saying this as a stainless steel engineer. The environments I work with are far more chemically hostile to stainless steels than simply going for a swim).

Just buy a sports band.

There are likely some properties of 316 L being used in the Milanese loop (It's the one Apple OEM band I don't own) That said, subjectivity to water is an enemy over time. I own stainless link bracelet in regular and black stainless with a plenty of water exposure, however, I do regularly ensure they properly dry to prevent any corrosion. I haven't had any issues as of yet after two years of owning both straps. But I do agree, consistent water exposure would be best for the flueroastamer band.

 

[ajm222]

Seems there are ways to make 316L more magnetic. The box clearly indicates it's 316L. Apple isn't going to put it on the box if it's not.

"Transformation from non-magnetic to magnetic phases

As both 316 and 304 stainless steels are austenitic, when they cool, the iron remains in the form of austenite (gamma iron), a phase of iron which is nonmagnetic. The different phases of solid iron correspond to different crystal structures. In other alloys of steel, this high-temperature phase of iron transforms to a magnetic phase when the metal cools. The presence of nickel in the stainless steel alloys stabilizes austenite against this phase transition as the alloy cools to room temperature. This corresponds to a somewhat larger magnetic susceptibility than we might expect for other nonmagnetic materials, but is still well below what might be considered magnetic.

However, this does not mean that you should expect to measure such a low susceptibility on any item of 304 or 316 stainless steel that you encounter. Any process which can change the crystal structure of stainless steel can cause austenite to be converted to the ferromagnetic martensite or ferrite forms of iron. These processes include cold working and welding. It is also possible for austenite to spontaneously convert to martensite at low temperatures. To complicate matters further, the magnetic properties of these alloys depend on the alloy composition. Within the allowed ranges of variation of Ni and Cr, significant differences in magnetic properties may be observed for a given alloy."

 

[Ixidor]

Seems there are ways to make 316L more magnetic. The box clearly indicates it's 316L. Apple isn't going to put it on the box if it's not.

"Transformation from non-magnetic to magnetic phases

As both 316 and 304 stainless steels are austenitic, when they cool, the iron remains in the form of austenite (gamma iron), a phase of iron which is nonmagnetic. The different phases of solid iron correspond to different crystal structures. In other alloys of steel, this high-temperature phase of iron transforms to a magnetic phase when the metal cools. The presence of nickel in the stainless steel alloys stabilizes austenite against this phase transition as the alloy cools to room temperature. This corresponds to a somewhat larger magnetic susceptibility than we might expect for other nonmagnetic materials, but is still well below what might be considered magnetic.

However, this does not mean that you should expect to measure such a low susceptibility on any item of 304 or 316 stainless steel that you encounter. Any process which can change the crystal structure of stainless steel can cause austenite to be converted to the ferromagnetic martensite or ferrite forms of iron. These processes include cold working and welding. It is also possible for austenite to spontaneously convert to martensite at low temperatures. To complicate matters further, the magnetic properties of these alloys depend on the alloy composition. Within the allowed ranges of variation of Ni and Cr, significant differences in magnetic properties may be observed for a given alloy."

I did bring that up in my previous post but I'll reiterate here, 316L is designed to perform best as an austenitic stainless steel (i.e. as a marine grade stainless steel), which is the design of its chemistry. Trying to turn it into ferrite/martensite using elaborate techniques is uneconomical as another magnetic corrosion stainless steel that is corrosion resistant could have been easily chosen (i.e. the entire range of 400 series and duplex stainless steels are automatically magnetic... and there are some with comparable corrosion resistance.)

Varying the Ni and Cr content would not cause a huge difference in magnetic properties. The defined chemistry of 316L renders it austenitic (it's designed to do so). It does however, change the temperature (but still below 0 degrees celsius) that a martensitic reaction could occur.

I'm not saying that Apple couldn't have done that, just saying that it doesn't make any engineering sense. Also, the milanese loop is REALLY magnetic, which is why I hesitate to believe that it's made of 316L.

Or maybe Apple did cold work the 316L to form the mesh... ... but to transform the entire thing into martensite, you'd need to be pretty hardcore... and since martensite is very brittle, this method would lead to excessive cracking. Hence I'd be surprise if Apple did it this way.

But who knows, Apple has many brilliant materials scientists.

 

[ajm222]

Did we consider the possibility that Apple used Neodymium ("rare earth") magnets in the closure? They're supposedly much more powerful magnets and would pick up even the slightest magnetism in cold forged stainless steel. They're the same kind of magnets used in the little satellite radio antennas that stick to your car. I often have a hell of a time lifting mine up and moving it. Extremely powerful but obviously cheap enough to use in inexpensive consumer products. I'd be willing to bet it's 316L but they are using a rare earth magnet in the closure.
[doublepost=1486390619][/doublepost]Actually, a quick search suggests this has been discussed before. Some others had the same thought about the type of magnet.

 

[Ixidor]

I don't have the official band but that shouldn't be too hard to verify. Just use a regular magnet on the milanese loop and see if it sticks as well the actual magnet on the loop.

But those bands are 150 USD after all, so maybe Apple really did some materials engineering magic here. At least compared to the 10 USD third party milanese bands.

 

[ajm222]

Stumbled upon this Apple copy as well, suggesting they also did some work with the metal itself.

"Based on a design developed in Milan at the end of the 19th century, the flexible metal mesh of the Milanese Loop wraps fluidly around your wrist for a perfect fit. Achieving the desired look required magnetic stainless steel. But off-the-shelf materials didn’t offer the necessary purity or corrosion resistance. So we created our own alloy and use a new thermal treatment that makes it more durable. The mesh is woven on specialized Italian machines, and every end piece is individually laser-welded to ensure smooth edges."
[doublepost=1486397040][/doublepost]I need to find myself a magnet...

 

[clauzzz203]

The magnetic force increases exponentially as the distance decreases. With a wide and close clasp area the band can make good use of the -probably neodimium- magnet