I've got a standard stainless steel Protex latch on my driver seat/box and it's absolutely fine. I've had the boat since November (I'm sure it's been on since build in 2003 as there are no other drill holes to give away previous catches) and it still looks shiny and works fine.
One of these: http://www.protex.com/27-1900SS-non-...-steel-natural
The only "problem" I had was that the safety catch was bent when I got it, and wouldn't lock the catch shut but a quick twist and all was sorted! (The catch is strong but flexible enough to easily manipulate with your fingers). I'm sure you wouldn't have any problems with not being able to unlock it.
Just think about where you put it though, as mine digs into the back of my leg if I stand up and brace myself against the seat/box.