Enable, Disable or Rename login SA in SQL Server

You can't change the permission of SA login in SQL Server:

change_permissions_failed_for_user_sa

You also can't drop the login SA:

drop_failed_for_user_sa

You can disable the login SA:

ALTER LOGIN sa DISABLE
GO

...or enable it:

ALTER LOGIN sa ENABLE
GO

You can rename SA login (renaming will not change the default SID which is 0x01):

ALTER LOGIN sa WITH NAME = [new_name];

After renaming a login, jobs owned by the renamed login may fail with the error similar to this:

'The owner (sa) of job syspolicy_purge_history does not have server access'

Restart the SQL Server Agent service if you got this error.

To check the name of a login when you know the SID, run the following query:

SELECT * FROM sys.syslogins WHERE sid = 0x01

To see how to enable, disable or rename other logins in SQL Server read related blog post:
How to Enable, Disable or Rename a Login in SQL Server