I've had Ni-Cd cells express a little bit of white powder past the
seams, but i've not seen that powder damage anything. I've been through
several computers, where "several" is on the order of dozens, not
hundreds. That doesn't mean it hasn't happened to you.

Leakage from alkaline cells isn't so bad, but the real killer is
leakage from zinc chloride (aka heavy duty) cells. That eats boards
alive. My brother and SIL have a SWR in which a zinc chloride cell
leaked. Nasty stuff. I ran wires to repair the board.