Securely erasing an external HDD won't actually securely erase - suggestions needed.

Hello, I'm attempting to securely erase an external 1TB HDD. Disk Utility correctly shows the drive and allows me to choose the level of security I want. I select DOE-compliant (3 pass) and it begins and completes the process, renaming the drive to whatever I choose, in about 10 seconds. Now I know Mojave is a pretty efficient OS, but it should take several hours of work to securely erase a 1TB drive. I ejected the drive, reopened Disk Utility, and repeated the process with the same result. I'm running 10.14.6 on a 27" iMac. Any thoughts?