Movement through a magnetic field will wipe credit and bank cards with a magnetic strip.
SD cards operate on a different principle. They are immune to magnetic fields. Unless it was as powerful as something like an MRI device.
Following link explains:
http://kb.sandisk.com/app/answers/de...,-magnetic-and
Water proof:
SanDisk SD, SDHC, microSD and microSDHC memory cards are tested to withstand up to 72 hours in 1m salt or fresh water; IEC 529 IPX7.
Product must be clean and dry before use.
Temperature proof:
SanDisk SD, SDHC, microSD and microSDHC memory cards are capable of withstanding operating temperatures from -13ºF to 185ºF (-25ºC to 85 ºC).
Shock and vibration proof:
SanDisk SD, SDHC, microSD and microSDHC memory cards are capable of withstanding up to 500Gs of shock.
Impact proof:
SanDisk SD, SDHC, microSD and microSDHC memory cards are able to withstand drops up to 5 meters (16.4 feet) and being run over by a 5 ton delivery truck.
X-ray proof:
SanDisk SD, SDHC, and Micro SD memory cards are immune to airport X-rays.
Magnet Proof:
SanDisk SD, SDHC, microSD and microSDHC memory cards are immune to magnetic field damage.