Crystals on a PCB?

Question

Electronics

I think many have come across cases when, after a small amount of rainwater got into the phone, as a result of electrolysis, crystals of something similar to salt appeared on the board, which made the phone buggy. Crystals can be washed off with alcohol, dry the board, and usually the glitch disappears.
Yesterday there was another such case: a push-button phone, as a result of "salt deposition" around one of the SMD components, began to "think" that headphones are always connected to it, even if they are not. Washing "cured" him of his "obsession", but this time I thought: where does salt come from in rainwater? Or is it not salt - and then what? What exactly is deposited as a result of electrolysis in the form of these crystals?

Answer 1

The question contains half of the answer.
On metal surfaces on which the liquid has fallen, the process of electrolysis occurs, solder and metals decompose to their salts.
That is why, after moisture has entered, it is necessary to turn off the battery as soon as possible so that there is no electrolysis, and then calmly disassemble, rinse and dry.