Turned the key and nothing lit up?

Cleaned corroded battery terminals on the vehicle, reconnected and tried to start, got groan from under neiththe dash but nothing else. Turned on the lights, but no power, turned the key and nothing lit up. No power period. Prior to first start in garage, the headlights would flicker on and off, then start, seconds later the front drivers side airbag light would be on and would not go out.