Car has been sitting on jackstands the last 3 months or so. Hasn't been started. I just pulled lower sparkplugs to put a few caps of atf in the chambers. The sparkplug ends (where the metal is) was covered in brown corrosion. I couldn't smell anything on them. It took a bit of filing to clean off the corosion.

Any ideas, or is it usual wear?

I changed them last summer(2003) (only had about 1500 miles on them, if that)

 

ya just sounds like normal burning and or carbon

 

Got pics?
Brown and glossy? powdery? First assumption based on the description in your post would be flash rust. Any orange as you filed?

 

actually under the brown was orange. It probably is flash rust now that you mention it, the car has been sitting long enough, and it has been snowing...

It looked powdery, but wouldn't come off without filling.

 

Yeah, "It fits the profile." Before you start it maybe shoot some some good penetrating lubricant into each spark plug location. My father-in-law swears by a product called "Kroil." He says it can free siezed engine blocks if you give it 48 hours. Marvel mystery oil squirted into each opening has always worked for me