Your memory card won't get corrupted unless you do one of two things:
1. Set more than 8 records at the Max Speed Test (game versions 1.0 and 1.1)
2. Memory card is removed during game save (or PSX freezes up during save, extremely rare!)
Again avoid the Max Speed Test!!! Do your top speed records at the Test Course race for Tuned Turbo No.1 cars, or get the records on the Arcade Disk (no serious bugs there).
Using anything more than a 1x card isn't always a good idea, either (such as 16x, or whatever). If the battery dies, you're out of luck. Get a second card (about US$7 nowadays) for backups.
Or get a DexDrive. I like it.