This..
"My samsung phone is so cocking awful (Galaxy s3) that it always has free storage, mainly because I try to use the phone as little as possible anyway. I'm now on my third SD card, and I've given up as all of them are now "damaged or corrupted" and the stupid phone refuses to ever use them again, and plugging them into a PC confirms that they're now faulty."
Means you have bought cheap shitty fake cards...
Fail to see how that's Samsung's fault...