Water damaged phone, boots up but screen not working

The phone got drowned ca. 4 months ago. It didn't spend much time in the water, it was quickly pulled out.

When I charge it up and try to start it, it vibrates and I see the LED diode flickering. It seems like a screen problem to me.

Today, I opened it, and I barely saw any damage at first. I first replaced the old screen with a new one. Doesn't work. I then noticed that a few pins at the edge of the screen connector on the logic board are black. I think this might be the problem.

Not really sure what it is, I think those pins got shorted from the water. I have no idea how to clean it.

So far I tried scratching it off with 99% isopropylalcohol and a knife, but it just doesn't come off.

I have submerged it into iso and it's sitting there right now, however, I doubt it's gonna help.