My phone doesn't turn on

Hi @franciskay

After that amount of time submerged you will be lucky to get it working again, but you can only try.

After cleaning the phone as described below you'll probably have to replaced the battery as no doubt it would be beyond recovery

The impurities in the water causes corrosion and provides circuit paths for the electricity which were not in the phone's operating design and could damage the components. The corrosion starts immediately and is ongoing until it is completely cleaned away

First do not try to charge or to turn on your phone and then remove the battery as soon as possible from the phone.

Then you need to dis-assemble the rest of the phone and clean all the affected parts using Isopropyl Alcohol 99%+ (available at electronics parts stores) to remove all traces of corrosion and water. If possible do not use "rubbing alcohol" as in some cases this is only 70% IPA or less, can contain additives which may leave conductive residues and is not as effective. If you do have to use it check the label to verify the amount of IPA. The higher the percentage of IPA the better

Here is a link that describes what happens. Electronics Water Damage

As always with electronics, especially surface mounted pcb be gentle when handling and especially when brushing away the corrosion. You do not want to remove any components from the board. Remove the shields that may be covering some components as the water may have got in under there. The ends of any flex cables and their connectors need to be cleaned as well.

Hopefully after you have done all this the phone might possibly work correctly again.

Here's a video that may help with the disassembly.

Here's the ifixit Samsung Galaxy A04 repair guide which has the service manual and a part list which may also help.

If this process seems too daunting, take your phone to a reputable, professional phone repair service, experienced in liquid damage repair and ask for a quote for a repair. If you decide to do this, do it sooner than later. Although in saying this most repairers won't try to fix it as usually with water damaged phones they cannot guarantee that it will continue to work once they they can get it to work if at all possible.