Yep you're dead right as it is very caustic......that's why it's best to select the heavy duty option so the longer rinse cycle flushes it nice and squeaky clean. (I usually give the alloy a liberal spray with Inox after to stop any further corrosion affects ;))
BTW - I only do this when SHMBO is out of the house and leave the dishwasher exactly as I found it :D:D

