After water gets into the laptop, Corrosion is a process, which converts refined metals to their more stable oxide. It is the slow and gradual deterioration of materials (usual metals) by a chemical reaction within their environment, In this case, the corrosion occurs when you combine electricity, metal, water and oxygen, creating iron oxide (or what is more commonly known as rust). There is no reliable timetable for this process to occur; a MacBook's internal components typically begin corroding immediately after the spill, but in some cases, your Mac can function normally for days or weeks without showing any obvious sign of a problem.  How fast the corrosion process takes depends on a ton of factors we have no control over, like humidity, the severity of the spill, and how long the device remained in contact with the liquid. The best practice is to not power on or use the MacBook at all until you can address the damage. Below are a few examples of corrosion caused by a water spill and how we repair.