Wednesday, July 15, 2015

Apple Watch and Water

Craig Hockenberry (comments):

Make sure you rinse your equipment in fresh water after it has been exposed to salt water. As you’ve seen above, that includes a swimming pool.


The biggest problem with the Workout app is that it’s basically unusable while you’re in the water. As we’ve learnt, both the touch and force press controls stop working. There’s no way to pause the workout. You have to start the workout before getting in the water and stop after you’ve gotten a chance to dry off.

For an ocean swim, this screws up your timing: you don’t really start swimming until after you get beyond the surf break. If there’s heavy surf, this can take several minutes. Workout data is being collected while you’re standing and waiting for waves to clear.


The elephant in the room: the touchscreen doesn’t work reliably anywhere near water. The source can be the ocean, a swimming pool, or your own sweat. At the same time, the Workout app is heavily dependent on touch[…] I’m convinced Apple’s recommendation to not use the watch in water is because of the erratic behavior it causes.

Dr. Drang:

The 316L stainless steel alloy Apple uses in the Watch is, as Greg Koenig said in this iMore article, quite resistant to corrosion. Your Apple Watch is extremely unlikely to develop corrosion pits or stains. But stress corrosion cracking, despite the word corrosion in its name, is a distinctly different phenomenon. SCC can break an object apart even as its surface remains bright and shiny.


316L is known to be susceptible to SCC in a chloride environment, like salt water or salt spray, so two of the three requirements for stress corrosion cracking, material and environment, are met. What about stress?


It is, I think, on the stress side that Apple is preventing SCC. By keeping the residual stresses low—or by making sure the residual stresses at the surface are compressive rather than tensile—Apple is eliminating one of the three requirements for stress corrosion cracking, and that’s why Craig Hockenberry’s Apple Watch won’t split open, even if he goes swimming in the Pacific every day.

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