Water is the enemy of wood. Water is also the enemy of cast iron. On wood, continued exposure to water leads to decay and rot. On cast iron, water/moisture leads to rust.
We’re woodworkers, so why do we need to worry about cast iron? Tools, man. Tools. That table saw table is likely cast iron, and so are other power tool tabletops. Over time, rusting is going to occur, and you’ll end up having to restore your table top.
Or, maybe you found an old table saw on Craigslist or at a yard sale. It’s covered with rust and needs a little love. You got a good deal on it; the motor still runs well, and it’s just a question of restoring it to its better days.
It’s not fatal, and with a few products and some elbow grease, you can bring that cast iron power tool table back from the seemingly dead. As with so many subjects in the woodworking shop, there are many different opinions and practices to consider, but we’ll stay with the ones we know work well.
There will be a need for a rust remover, and there are a number of products available for that part of the process. An abrasive of some type will be used to work with that rust remover, too. Just as in our woodworking practices, though, the surface must first be prepared for the rust remover and treatment beyond to restore the cast iron to a shiny and smooth finish.
Remove Loose or Raised Rust
The coat of rust may be heavy, and some of the raised areas will need to be scraped. Nothing more than a putty knife will be needed for this task. Go lightly, though, so as not to gouge the surface beneath.
Wipe away everything that is loose after the scraping. It isn’t necessary that the surface be too clean; after all, there’s more work to be done, and that’s going to be a little messy, too.
Rust Removers for Cast Iron Table Tops in the Shop
There is a pretty long list of rust removers to choose from, some specific to the task, some usually used for other tasks. You might have your favorite, but we’ll offer a few for your consideration.
- Evapo-Rust Super Safe Rust Remover. It’s biodegradable, powerful, and safe. It will rid most anything of rust – including cast iron – and the manufacturer claims it will not require sanding or scrubbing. We don’t know about that claim, but we found a number of sources who recommend the product. It’s non-corrosive and has no odor, and can be poured down the drain, even. It needs no dilution and can be used straight from the container. Although it is one of the car enthusiast go-tos for rust removal on cast iron car parts, it works well on cast iron generally and could be used on your table saw top.
- Naval Jelly. It’s made of water, phosphoric acid, and sulfuric acid. It works by dissolving rust and turning it into something kind of gunky that you can simply wipe off. Although it sounds like something the navy would use when getting rid of rust on naval vessels, it’s simply a general rust removal product. It’s been around now for about 40 years. Loctite makes a version of it, for instance, and we know Loctite from a piece we wrote about glues that you will find here. Gloves and goggles are highly recommended – it has acids in it. Be in a well-ventilated room, too – again, it has acids in it.
- Rust-Oleum Rust Stripper. As you’d expect from a brand called Rust-Oleum, it offers a rust stripper. Rust-Oleum products are not just for preventing rust but also for removing it. It, too, is a naval jelly product and is easily found in the big DIY stores as well as car care stores. Again, gloves and goggles are highly recommended. And again, a well-ventilated room – acids, we said.
- WD-40. While WD-40 also makes a rust removal product, we suggest you consider the straight WD-40 for your cast iron table saw top. It won’t work like naval jelly, which is simply applied and allowed to sit and turn rust into gunk; there will be more work required, most of it from your hands, but it is a viable rust removal lubricant.
- Mineral Oil. Also, a good lubricant for the abrasive that will follow. It’s a liquid byproduct of refining crude oil that is an effective lubricant for many purposes. Although not for use on cast iron, baby oil is a petroleum-based mineral oil, also a byproduct of the refining process.
These aren’t the only rust removal products, of course. Each has its own value in removing rust from cast iron table tops, though, and should be examined to determine which you will prefer.
With all of these products, especially the naval jelly choices, be sure to read the labels carefully for instructions and follow them closely. For instance, you’ll find that naval jelly shouldn’t be left on the surface for a long time, nothing more than 15 minutes and then washed away with water.
Abrasives for Removing Rust From Cast Iron Table Tops
Now that you’ve chosen a rust removal product that can act as a lubricant (except for naval jelly), it’s time to pick the abrasive. The choices include:
- Steel wool. While this can be an effective abrasive, it can leave fine scratches that you might want to avoid. Others might like the brushed metal look and be willing to go with steel wool. Your choice.
- Sandpaper. The same holds true for sandpaper, another effective abrasive but one that could leave fine scratches no matter the high-numbered grit you choose. Your choice.
- Synthetic scrub pads. Something like a Scotchbrite or something along those lines would be a good substitute for steel wool or sandpaper. They are less likely to leave fine scratches and still work well.
Whatever abrasive you choose, you know what comes next. Steel wool and synthetic scrub pads are hands-on scrubbing items, while sandpaper can be used with a random orbital sander unless you want the hands-on experience of a sanding block.
Go to work, scrubbing the entire surface of the cast iron table. Take advantage of the lubricant rather than attempt dry sandpaper. The lubricant will, in many cases, soften the rust and make it easier to remove.
Finishing the Table Saw or Other Cast Iron Table Top
Scraping, lubricating, and scrubbing are all done, and paper towels will remove either the gunk (if you used naval jelly) or lubricant and rust particles from the surface. What’s next?
After going through all of that work to restore the table top, you’ll want to do something to prevent rust in the future. The first thing we suggest is to use a rubbing compound – another automotive care product – or a metal polish and a buffing wheel to give the surface a smooth and clean finish. Wipe it down with a solvent like acetone until the wiping rag comes off clean.
Beyond that, though, there are a few products you might find helpful for the final part of the process:
- Boeshield T-9. This product, developed by Boeing, will provide water-proof lubrication and protection against rust. The water-proof part is clear, of course, but the lubrication is for another necessary finish – you want the wood to slide smoothly across the table saw top or any other power tool table top as you push it through the blade. It’s a waxy rust-prevention substance that will give about 6 months of protection and lubrication before another coat will be necessary.
- SlipIt. This is a sliding compound that will give your cast iron table top the lubrication it needs for the wood to move smoothly along the surface. It’s odorless and greaseless and will protect the cast iron for a few months before another coat is required.
- Johnson’s Paste Wax. Often sold as a floor wax, this will give the cast iron surface a waterproof finish that lubricates the table top for the wood’s smooth gliding. It’s long-lasting and easily reapplied when necessary. The cast iron is bare, so it will need two coats to make sure the entire surface is protected. Allow it to sit for 20 minutes, and wipe it off each time.
In this video, it’s a band saw table with rust, but it is cast iron, and the technique is effective. The videographer chose the WD-40, Scotchbrite, and Sandpaper method with great success. He chose Glidecote for his final coating, a product made specifically for the purpose, although we would prefer a Johnson’s Paste Wax finish since it is a product we know and like.
If you see an old table saw, or band saw with a rusted table on Craigslist or at a yard sale, don’t shy away from it. With a little bit of smart work, you can bring it back well and have yourself a great bargain in the process.