Basically, flood and water damage to electronics fall into one of three categories: submersion, direct hit, and high humidity.
1. Submersion: Electronics are completely covered with standing water and/or mud type sediment from a few short minutes to days.
Replacement is recommended in these situations for several reasons. If the power to the unit was on when the water damage occurred, the chance of an electrical short to the piece of equipment is highly probable. This type of damage would require parts replacement as well as cleaning which may not be cost effective, unless the equipment was of a commercial grade, such as routers, or audio/video equipment.
Often cleaning can restore this equipment because very little water may have gotten inside the components themselves. It may look worst on the outside than it actually is on the inside. If nothing were done to the equipment, and left to dry on its own, it may work for a short time, but eventually contaminants and/or minerals left behind by the water will cause corrosion on circuit boards. Realize that corrosion can be stopped, but not reversed.
3. High Humidity: This would include standing water in a room with electronic equipment such as a basement, a home theater, a computer lab, etc. Usually this equipment is off the floor on a table, desk, or entertainment console.
Because of an increase in humidity, electronics in the area may be adversely affected. Dust is the enemy in this case. If high amounts of dust are present in the equipment, the humidity settles on top of the dust, creating a “mud” type of sediment that will cling to circuit boards. Cleaning is required.