Promotes Rust

[RedFord150]

I use Soft Pistol cases (Gun rugs?) inside of my safe. My handguns have to stack, I do not have enough shelf space for everything.
Only 1 or 2 of the cases have a fleece lining. Most are a simple fabric with some padding. So far, I have never had a rust problem. Owned this safe for around 10 years and some of the guns over 20 years. Before the safe, they got stored in same soft cases, but inside of a wooden locking desk drawer.
Some guns are blued, some are stainless.

[badfish71]

another +1 on the safe and dehumidifier

[Cyphre]

I'd say the general warning is that those black (or grey, or whatever color) open-cell foam cases is that they aren't environmentally sealed, other than higher end Pelican or others approved for airlines. The foam itself is definitely nice early on, but when it deteriorates, it is really messy and terrible. Unless the case in question is somewhere that is already environmentally controlled (like the aforementioned safes with dehumidifiers), the foam itself basically dries up, turns brittle, and turns to dust. What is worse, however, is when it sticks to just about any surface it was in contact with. It's probably not as common nowadays, but that old foam gets pretty raunchy after a while. Mind you, a longer period of time, but fairly short in regard to the overall lifespan of a firearm. Open cell foam also holds moisture, as mentioned, as opposed to close-cell foam that you'd find in such things as el cheapo life vests. Not quite as forgiving a material, however.

Silica Dessicant and gun socks definitely remove the worry in storage.

[Vampyredark]

I just put a dessicant pack in with my revolver. However, what about a strait up plastic case that came with my ruger - no padding or nothing. Just cheap-o plastic case; gun bangs around and everything, LOL.

Well, just what about that case. Should I still use a dessicant pack. I will have to find another one somewhere....

[Hopalong]

As with any metal tool, the best rust preventative is use.

Which usually means a wipe down or cleaning along with it.

I put my guns up in Bore Stores in a safe, with a rechargeable desiccant thingy.

I've never had a bit of rust on any of my guns, and I've used all kinds of different cleaning products on them.