Why won’t it turn back on?

Hey all I recently purchased a water damaged iPhone 5 off of a friend and it was certain it wouldn’t work again but for some reason when I put a spare screen on it, it turned straight back on but then I was curious so I put the old one back on to see weather it would work but it wouldn’t so I put the spare one back on with no success of it booting back on, there was some corrosion on the board connectors so I cleaned them, I’m certain I didn’t fry the board as it is still drawing just under an amp and that’s what it was taking last time, so I am leaving it on charge overnight to see if it somehow comes back to life but if not does anyone have any ideas? Thanks!