Will the pins corrode touching my sweating wrist?

The connector should be ok as long as you take care not to connect the charging cable while the connector is wet or dirty.

Can't say I see any corrosion - had this one about a year and its been subjected to sweat (a lot of), bug spray, sun tan lotion, etc. Not used a screen protector either - though I don't do a job that would bring the watch into contact with other things that much. Bashed it plenty on trees, doors, though and not seen any scratches - that said, they can scratch, so if a 3 dollar cover helps, then no harm there. Back cover would keep out the dirt too - I just wash it daily (for the most part) with good old soap and water and its been all good. Not had the legendary sensor cracking either... yet.

i bought them on eBay from china 2euro for six
with shipping
they are small and easy to lose
the connector starts to get really dirty after a wile with no cover

Great thanks for your input guys....