Selling water damaged MacBook Air 2017: Is it safe to simply remove the SSD? I water damaged my Macbook Air 2017 and it will no longer turn on. I was thinking of selling the MBA for some money but wanted to make sure that my security is not compromised. 

If I remove the SSD from the motherboard (and sell it without the SSD), am I safe to assume that none of my personal data is still on the laptop?
Yes, you can assume that none of your data is still on the MacBook Air. All personal data stored on the laptop itself is stored on the SSD, so removing this effectively removes the data from the laptop.

It is also possible that the SSD is still fully functioning, so if you made the mistake of not backing up your data, you may be able to still access it from the SSD, via adaptors, external enclosures or another MBA of the same generation.

You may also want to refer to Apple's advice on what to do before you sell, give away, or trade in your Mac.