Having designed and troubleshot military electronics, I know corrosion can show up any time something is exposed to weather.
So what I do for wiring is to paint any metal surface that is exposed. It also helps to use heat-shrink tubing everywhere posssible.
When using electrical tape, DO NOT STRETCH IT. It will only get loose with time, expose metal and make a mess to boot.
On batteries, I grease any metal except the actual connection surfaces.
On both of these areas, it takes some work to get to the undersides and backsides of exposed metal, so work it, work it.