Encrypt SD card
SD card encryption is a default Android security feature. Enabling SD encryption is a very straightforward process, and many phones even have it enabled right out of the box. In order to complete the encryption process, your phone must be unrooted, plugged in and have at least 80 percent battery remaining.
If the process is interrupted for any reason, you’re likely to lose access to all the data on your device. Thus, it’s advisable to run a full backup first, just to be safe.
Go to Settings -> Biometrics and Security -> Encrypt SD card.
Tap Encrypt SD card.