Not turning on from power button

Hi I'm new Mac's, dare I say am a PC guy, I was asked to have a look at his mid 2011 iMac that was having issues, he was having problems with it starting from the power button then eventually it wouldn't start at all even with every reset known, when I opened it up I discovered there was water damage (corrosion) to the logic board especially around the smc chip (this came from being stored in a Damp room). It has cleaned up really well but cant get to the underside of the SMC chip bga

I cleaned the best I could but with still no joy, but I discovered that if I remove the Pram battery ( I call it the cmos battery) and reinstall it and plug the iMac into the main power the machine boots to its desktop and runs without any issues it turns on without touching the power button at the rear.

I have taken some pictures from an area on the board that looks suspect to me the two components look like they are shorted together with solder can anyone confirm if this is the case on this Logic board

I've replaced the power supply with a new one so that's ruled this out, the power button also checks out with the multimeter so no issues there, can someone explain why this wont turn on from the power button

any you guys shed some light on the issue

Thanks in advance

Sorry the board is a 820-2828-a 27" mid 2011