Submersion. Electronics are completely covered with standing water and /or mud type of sediment from a few minutes to days. Replacement is usually the best course for these situations for many reasons. If power was on at the time of the water damage, chances are electricity caused a short to the equipment. This would require parts replacement as well as cleaning, which may not be cost effective unless the electronic equipment is high end such as commercial switches, routers, audio and video equipment.
Direct Hit. Technology that had water rain down on it or was splashed by running water from a loss nearby. Many times this equipment can be cleaned because very little water may have gotten inside the components. It may look worse on the outside than on the inside. Cleaning would be recommended for these components to remove any contaminants left behind by drying water. Corrosion can be stopped, not reversed.
High Humidity. This includes standing water in a room with electronics such as a basement, home theater, server room, computer lab, etc. Usually the items are off of the floor on a table, desk or entertainment center. The equipment was not hit directly but may have been in a room that had a huge spike in humidity. If a water loss occurs and dumps water into a room and jumps the humidity to 90%, the electronics in the area could be affected and need a proper cleaning to live a normal life cycle. Dust is the enemy in this scenario, high amounts of dust inside electronic equipment is usually not a major issue aside from the fact that it doesn’t let the circuit boards “breathe” properly which could cause overheating issues. On a normal basis, dust could be blown out. Once high humidity is introduced into electronic equipment, it settles on top of the dust forming a “mud” type of sediment that will cling to the boards. This dust will not sit lightly on the boards, but stick to them until removed by cleaning.