How can I fix S6 edge liquid corrosion?

Hi, I dropped my Samsung Galaxy S6 Edge in hot spring water. I didn't notice at first so it stayed there for more or less 3 minutes. When I recovered it, the phone was off so I immediately placed it in uncooked rice for 24 hours. It still wasn't functioning so I sent it to a Samsung Service Center. They said the motherboard and battery needs to be replaced. I didn't proceed with the repair since it was quite expensive. When I got home, I tried charging it and to my surprise it worked perfectly fine. After two days though, the phone won't turn on unless plugged. When I try to unplug the phone, it shuts down but when plugged, it sill works fine. I tried the function test (*#0*#) and everything worked fine. I sent it a different Samsung Service Center and they said the motherboard, battery, LCD and rearcase need to be replaced because of liquid corrosion. I asked if it was possible to just change the battery since the phone was working fine except for the battery but they refuse to do so saying its hard because of the liquid corrosion.

What fix can anyone suggest? I want to try fixing it myself. I can't afford a motherboard replacement and the phone is fairly new so I want to try whatever's possible to fix it at a minimal cost.

I'll appreciate all the help I can get. Thanks!