We hiked for about an hour and a half in wet overcast/misting conditions.
I take this thing on hikes and on bike rides (I have carried it non-stop for the last ~2 months), it gets wet and sweaty all the time. I have not once concerned myself with rust.
I guess I am lucky because only once have I noticed any staining (near the jimping on the spine of the blade where my sweaty thumb spent a lot of time during a carving session...I spent an hour carving a spoon).
On 2 occasions I hosed the knife down with WD-40, but this was to attempt to flush out fines from when I ground down the liners. Other than those occasions, I have never done anything other than use it and wipe it on whatever was handy (usually a shirt tail).
Honestly, I expected this knife to stain and rust by now...I have treated it like an enemy that owes me money for 2 months now and the only "character" I can give this knife was done with abrasives while it was clamped in a vice.
I have nothing in the way of "data" but it seems that some people perhaps secrete more caustic chemicals than others....Mine must be fairly neutral? Regarding nature and the exposure to elements here in Missouri...M4 seems to resist corrosion fairly well.
Not arguing anyone else's findings or frustrations...just stating that *I* have had nothing adverse in the way of staining/rusting with M4.
