I carried one IWB for a year or two and found that it would start to rust on the inside of the yoke if I didn't wipe that area down every night with a silicone cloth. The yoke and cylinder are steel, but only the yoke rusted.
I switched to a 640, then a 649, and now carry a 632 (basically a 6-shot 642 in 32 H&R magnum) and never had a hint of rust with any of 'em, even though I never wiped 'em down at night. Personally, if I wanted a lightweight hammerless 38 again I'd pick the 642 over a 442, just because of my experience with rust.
I switched to a 640, then a 649, and now carry a 632 (basically a 6-shot 642 in 32 H&R magnum) and never had a hint of rust with any of 'em, even though I never wiped 'em down at night. Personally, if I wanted a lightweight hammerless 38 again I'd pick the 642 over a 442, just because of my experience with rust.