I've got a micrometer I don't use often (A Central Tools 2 - 3" micrometer) so I'd like to put it away properly so it will be protected and ready for use. So should I get some desiccant ( a bag of 'Do Not Eat!") and seal it in a freezer bag or what? My shop and office aren't particularly humid but sometimes things happen, even in the best families!
A desiccant along with keeping out moisture works, as does VPI paper. Coating tools with a stable oil with anti corrosion additives like ATF also works for tools in more general use. I live in Sacramento, California, and it is essentially an irrigated sub-desert, so I definitely have it easier than most of us, and some of my methods may not work as well in humid and/or coastal areas. Keeping tool storage areas at a temperature well above the dew point (or lowering the dew point by keeping the relative humidity lower) is a basic of fighting corrosion...
Get you a bottle of Starrett M-1 oil. Or get the airesol can of M-1 oil and use on your tools. I keep a case of it on hand as much of it as I use for just about everything. Little Machine Shop sells it and usually has the best price for it that I've found. Ken
I run two sets of outside mics.
One set is at my surface plate. I use them exclusively for inspection in that area. I work at wiping them down after each use.
The other set I drag around the shop. This second set is potentially subjected to a lot of abuse including accidentally dropping.
This second set is a mix of what ever I could find a hot price on. While I try to take care of them. I don't go nuts.
I heat my shop to at least 55degrees F year round.
Because I don't run AC in the summer, my biggest problem seems to be my own salty sweat. It leaves permanent fingerprints and rust.
Even skin oils in the absence of sweat seems to leave a mark.
I use a light oil like WD 40 to wipe them down and I keep them in their protective boxes/sleeves or whatever they came in. I've had to make a couple of boxes as well for some "homeless" tools I've picked up. I keep all of my calipers, rules, squares and such with no protection in a special drawer with a felt liner and a dozen scattered desiccant bags. Most all of my mics were purchased in the 80's and they still look new.
But I live in SoCal. I'm sure you have to be extra diligent in high moisture or humid environments.
If you absolutely, positively must have your tools rust, coat them with WD40 and then forget them, come back months later and enjoy that beautiful patina of red/brown. Instrument oil for instruments and M1 for everything else. This has worked for me for years.
T-9 BoeShield, Starrett Tool oil and Dow Corning Molykote Metal Protector and Vci paper work for me.
The DC Metal Protector is great because it;s a thin wax film, wax in solvent. All oils will dissipate after a while and you will get rust., or worse.
Investing in a dehumidifier is a good safe bet too.