Yes, you can.
On an iPhone go to Settings/Screen time and set a code for screen time. Tap App Limits, tap Add Limit and enter your code, tap Social select Angelchat and set a limit on e.g. 1 minute. Now, you'll need to enter the pin each time you open Angelchat.
On an Android we recommend that you install an app from SuperTools called AppLock, which allows you to set passwords on specific apps in your phone.