Wireless power transfer through stainless steel
It's not its magnetic properties that are the problem - it will have induced into it AC eddy currents that will pretty much kill off your magnetic field. I don't think you'd get 1 watt through 1 mm SS let alone 12 mm unless you were operating at 10 Hz (that's hertz not kilo hertz).

EDIT (not related to the question) - you'd be surprised about the odd magnetic properties of "mm sizes" of 316 SS at between 50 kHz and 1 MHz, specifically 300 kHz. Just stuff I've observed when designing food and pharmaceutical metal detectors.