How to Remove Cosmoline

Dealing with The Protective Coating From Hell

Last update: 11/20/09

I've always heard it called "Cosmoline". According to Wikipedia, it's a generic name for a whole class of rust-preventative coatings. Of course, Wikipedia is often politically-correct and dead wrong, so take that with a large grain of salt. There's a company that makes an actual line of products named Cosmoline, but they describe the rust preventative as a "colorless, thin film" which is definitely not what I'm talking about. Regardless of what it is, for the sake of tradition and convenience, let's just call it Cosmoline.

If you've ever gotten a new piece of equipment with a cast iron top, you know what I'm talking about. Thick, brownish-yellow, sticky, just plain gross. It appears that it gets sprayed heavily onto the top after finishing. It's sole purpose is to prevent that beautiful new top from turning into a rusty, pitted mess during its trip to you. Here's an example from a recent piece of equipment I bought

In this case, the manufacturer also put a piece of plastic over the Cosmoline, hence the strange patterns.

Sometimes Cosmoline is like a thick oil, sometimes more like the coating on a candy apple (but not nearly as tasty). Depends on how "factory fresh" the machine is, I guess.

To say that Cosmoline is hard to remove is an understatement. In fact, its resistance to cleaning is almost legendary.

Over the years, I've tried lots of different things to remove Cosmoline. Most people try some form of acetone like paint thinner. They work OK, but they dry out really fast, which makes it hard to soften up the large chunks and globs that are down in grooves or slots. And, since they flash off so quickly, they let a thin layer of dissolved Cosmoline dry back onto the surface as you're wiping, making it really difficult to get the stuff completely off.

Also, paint thinners and removers like acetone have another bad side effect: they remove paint, which isn't surprising since that's their real purpose. Many if not most cast-iron tops have their edges painted and it doesn't take much to ruin the nice glossy finish or start completely taking the paint off.

And, let's not forget the noxious smell and the fact that's it's really bad for your lungs and poisonous. Oh, as a bonus, it's also extremely flammable!

There is, however, one product that I've found that's absolutely perfect for removing Cosmoline: WD-40! But wait, you say, WD-40 is a lubricant. Sorry, Grasshopper, but that's not true. Many people think it's a lubricant because they use it to loosen rusty bolts, but actually it's primarily a solvent. It penetrates and breaks down the rust, it doesn't oil it up. It apparently does contain a little oil of some kind, but not much.

Not only does WD-40 dissolve the Cosmoline, it does it better and faster than acetone. I really like the fact that it doesn't dry out, but sits there and works on softening up the Cosmoline. The spray and handy tube make it easy to get into grooves and slots, as well as bolt holes. Also, while acetone strips the metal completely bare, WD-40 leaves behind a slightly oily residue that repels moisture and protect the cast iron for a little while until you can get around to protecting it with something like Topsaver.

To clean a new top, I spray the top liberally with WD-40 and smear it around with my fingertips, so that all parts of the top are very well-soaked. You'll see the Cosmoline start dissolving immediately (it's really rather disgusting). Let it sit for a minute or so, then start wiping up the goo with some paper towels (did I mention it's rather disgusting?). You'll probably be left with lots of spots where the Cosmoline was thicker, just keep spraying and using paper towels to scrub at it. A plastic scraper can also be helpful with heavy globs. Don't use a steel or razor scraper, no matter how careful you are you will gouge the top. After 5 minutes or so you'll be left with a bright, shiny, Cosmoline-free top.

Tops with slots like tablesaws need some special attention. Getting into the corners of the slots, especially if they're T-slots, is tough. I use the spray tube to get the WD-40 soaked into the slot, then use a brass-bristled cleaning brush to thoroughly work the slots and get the Cosmoline out of the corners. I find the brass brush does a good, aggressive job of cleaning without scratching up the cast iron. It also works really nice on areas that aren't machined as nicely as the top, getting Cosmoline out of deep milling marks is much easier with a good brush. Just don't get a large one, get the kind about the size of a toothbrush.

After you get your top nice and clean, don't forget to protect it. As I said, WD-40 is a solvent. Despite it's somewhat oily feeling, it's not a lubricant and it's not a long-term protector. A day or two is OK, but you really need to use a product designed to seal the metal and ward off moisture. I've used both Topsaver and T-9 Boeshield, as well as Johnson's Paste Wax. I use both TopSaver and JPW. I just don't like the thickness of the coating left by T-9.