How to prevent humidity damage in your macbook.

This is not going to be easy as you have to regulate the relative humidity in which the device operates. That would be using it only in an air conditioned environment, having a room dehumidified or maybe just keeping air moving over the device at all times. The fix is likely to be trial and error; I suggest you invest in a good humidity indicator.

Unfortunately, all the above pretty much negates portability. I can tell you trying to seal the unit will not work. Air needs to flow over the unit as well as through the inside.