Alpha Masking

Hey Guys, For compositing purposes, I was just wondering if I can disable the alpha channel for an object?

For example: I want to create an object which is opaque but it appears black in the opacity channel. So I can select an object in a current via the alpha map channel

This would be hypothetically used for CGI compositing.

No, but if you wanted to you could apply materials in a way to give you a pass that does what you want, basically rendering again with objects hidden or give a black or white unlit material