New here but have been sharing your pain with the whole "damaged SD card" thing.
I've had this a couple of times on my Galaxy Ace and the last time it happened I used the chkdsk/x/f trick and it worked a treat.
However, yesterday I was playing some music through the phone but I found that you cant stop the music, only pause it so I did a full phone switch off. That certainly stopped Fleetwood Mac but also appears to have wrecked the micro sd card as well - the dreaded "damaged SD card" reappeared.
I wasn't too concerned as I thought the chkdsk thing would work but IT DIDN'T!
The thing is that the when I put the micro sd into the sd card reader and hooked it up to my pc (running XP) the card was fine - everything was readable so the chkdsk command had nothing to put right.
In File Manager I ran Properties and did the whole scan disk routine, I even scanned the card with AVG. Nothing would induce the phone to mount the card. I put it in my Samsung Tab 2 - same fault appeared, back in the pc - working fine.
So I ran the Backup utility in File Manager and created a copy of everything on the card and saved it to my pc hard drive, and then copied the backup onto another micro sd card and mounted that in the phone. Everything worked fine - the photos were there, Whatsapp messages reappeared, camera worked. Result.
Next I reformatted the original sd card in the phone (ie wiped it clean - do NOT do this until you have checked and confirmed you have a workable backup copy elsewhere) then safely removed the card, loaded it back into the pc, copied the backup from the pc to the sd card, remounted that version - and again everything worked!
I have absolutely no idea what the fault was as the card worked on the pc but not in any android device. The only fix was to reformat and start again.