I've got some old tools in my garage that are starting to get rusty spots, and I'm trying to figure out if there's a way to actually prevent this from happening. Is it just moisture, or is there more to it chemically?
Are your tools bare metal or do they have any coating on them already? Rust happens when iron reacts with oxygen in the presence of moisture - all three need to be there together, so you can prevent it by removing any one of those. For your garage tools, the easiest approach is keeping them dry (wipe them down, store in a dry spot) and coating them with something that blocks oxygen and moisture, like a thin layer of oil, paste wax, or even spray lacquer depending on how much you want to fuss with them.
i've had to deal with this myself - left some screwdrivers and wrenches sitting in a damp garage for a few winters and they started pitting pretty quickly. the chemistry is indeed more than just moisture alone. iron rust (iron oxide) forms when iron atoms lose electrons to oxygen, and water acts as the electrolyte that makes this electron transfer possible. you technically need all three: iron, oxygen, and moisture. but here's the thing - even if one answer said you can prevent rust by removing any of those three, that's easier said than done with tools you actually use. you can't really remove the iron from a steel tool, and you can't eliminate all oxygen from your garage.
the practical approach is to focus on moisture and create a barrier. keep tools dry - store them in a low-humidity space or use silica gel packets and airtight containers. if moisture does get to them, wipe them down regularly. the real workhorse solution is coating: a thin layer of oil (even basic 3-in-1 or gun oil works fine) prevents water from reaching the metal surface. some people use paste wax, which stays put better than liquid oil and doesn't drip everywhere. for tools you use often, a quick wipe-down with an oily rag every month or two will keep them in good shape. if rust has already started, you can remove surface rust with a wire brush or steel wool, then immediately oil it before moisture creeps back in.
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