Rust Busters

If time is a monster that devours all things, then rust, also known as oxidation, is its teeth. Rust attacks everything from fabrics to plants to rocks. Even our bodies are constantly under attack, and if it weren’t for the presence of certain substances within our cells, we’d all dissolve from the corrosive effects of oxidation.

But it’s with metals, especially iron and steel, that we see the most dramatic effects of rust. Unprotected metals can develop rust in as little as a few hours, and once established, rust can be devilishly difficult to eradicate.

But just because rust has taken root doesn’t mean that all is lost, there are seven effective ways to correct the problem on almost any metal surface. Some are best suited for delicate or valuable metal pieces such as firearms or hand tools; others are ideal for heavier, utilitarian objects such as fences and flagpoles. No matter what type of item you’re trying to rescue, one of these techniques will help you to restore its gleaming glory.

Method 1: Abrasives
The simplest way to remove light surface rust is with an abrasive material such as a sheet of sandpaper, a wad of steel wool, a pumice stone or a ball of crumpled aluminum foil (which works great for removing rust from chrome). Sandpaper, combined with a flat or molded sanding block, can be quite effective at removing minor surface oxidation as well as heavier rust, but it requires a lot of patience and repetitive motion. Aggressive papers such as 80- and 100-grit can remove heavy rust buildup, but they will easily scratch many metal surfaces. Finer sandpapers in the 300-grit range are best suited for removing light surface rust without heavily scratching the underlying metal.

Many rotary tool attachments are available for dealing with rust. Shown here are Dremel’s abrasive flap wheel, general abrasive wheel and grinding wheel.

If your prime objective is to avoid scratches and preserve the original finish as much as possible (on woodworking hand tools or firearms, for example), sandpaper is far too damaging. Instead, use a 000 or 0000 steel wool pad. Apply light machine oil to the surface of the workpiece and gently scour it until you remove the corrosion.

For delicate metal surfaces, use 000 or 0000 steel wool combined with a light application of machine oil to scour away surface oxidation. Work in small circles and immediately treat the cleaned area with a fresh coating of oil.

Method 2: Brushes and wheels
Wire brushes and abrasive wheels — whether hand-powered or motor-driven — are the next, more aggressive step in removing rust. These implements use friction to loosen damaged surface particles and lift them away from the base metal.

A wide variety of wire brushes is available in many different sizes and materials. Be aware that if the brush is harder than the workpiece, you’ll scratch the surrounding finish as you remove the rust.

In addition to the hand-powered variety, wire brushes and abrasive-wheel attachments for power tools are available in a variety of sizes, grits and styles. Small wheels made to fit rotary tools are best suited for smaller workpieces, tight spaces and delicate applications. Larger brushes for power drills and angle grinders are available as wheels, discs, cups and end brushes.

Wire wheels and brushes are available for power drills and angle grinders. Shown here are a cup wheel for a drill, a wire disc for a drill and a wire disc for an angle grinder.

Whenever you work with these tools, follow a few simple safety precautions. Always wear eye protection because the spinning implement can fling rusty bits into your face. And be aware that the rotational force of a powered brush or wheel can be substantial – if it inadvertently grabs the workpiece, it can cause the drill to kick back and wrench your wrist.

Method 3: Surface treatments
In cases where the rust is too firmly established to be easily removed, one option is to treat it with a coating that will keep it from spreading. Specialty primers block rust from the surrounding air, cutting off the supply of oxygen. Other treatments can convert existing rust into an inert, nonrusting material that can then be primed and painted. These primers and treatments are as easy to apply as any other type of brush-on or spray paint – just be sure to follow the manufacturer’s recommendations for drying time and application of topcoats.

Method 4: Chemicals
For stubborn rust or in cases where it’s important to remove all traces of corrosion, chemical rust strippers will often provide satisfactory results. Most products that advertise the ability to dissolve rust use oxalic, phosphoric or sulfuric acid to etch the surface and expose new metal. Because of the harmful properties of these acids, you must use extreme care when working with them. Follow the products’ recommended safety procedures, and always store any unused product as directed by its instructions.

A less hazardous option is to use a product that works through selective chelation. In this process, the rust is broken down into molecular components and lifted away from the base metal. These products can remove even deep rust from mild steel and iron. Evapo-Rust claims to be biodegradable, nontoxic, noncorrosive and harmless to copper, brass, wood, plastic, rubber or vinyl, so you don’t have to disassemble a rusty item before submerging it. But because the process requires complete immersion, you’ll have to purchase a substantial amount of the solution for it to work.

Through a chemical process called selective chelation, treatments such as Evapo-Rust remove rust from the metal surface. The process requires complete immersion of the workpiece in the chemical.

Method 5: Electrolysis
One of the most effective ways to permanently rid a metal object of corrosion, electrolysis uses the reaction between a small low-voltage electric current and a suitable electrolyte (solution) to convert surface rust back to metallic iron by physically reversing the chemical process that allows rust to develop.

Because it poses significant safety hazards, electrolysis is most often performed by professional restoration shops, but it is possible to do it yourself. You’ll need a plastic tub, an iron electrode, water, washing soda and a battery charger. To make the washing soda, add about 1/3 to 1/2 cup of soda for each 5 gallons of water. Do not be tempted to use more soda to make a more concentrated solution, it’s the electric current, not the amount of soda, that removes the rust. And because the process releases explosive hydrogen gas, never try it indoors. Set up the equipment in a well-ventilated area where’s there’s no chance of a spark.

The basic setup for electrolytic rust removal includes a plastic tub, a solution of washing soda, a steel electrode and a battery charger. Make sure you hook the red terminal to the electrode and the black one to the workpiece.

Make sure the battery charger is turned off; then connect the positive (red) terminal from the charger to the iron or steel electrode and the negative (black) terminal to the workpiece. Be careful, reversing the voltage will dissolve the object you’re trying to restore. Submerge the rusty item in the solution; then insert the electrode into the tub so that it partially protrudes from the solution.

Set the charger to a low charge rate and turn it on. You’ll know the process is working when you see small bubbles rising from the workpiece. Moderately rusty objects will typically need a few hours to come clean; heavily encrusted pieces may need to be left overnight. When the bubbles stop forming, the object is generally rust-free. Shut off the power, remove the workpiece from the solution, rinse it thoroughly and immediately treat it with a light coat of oil to prevent flash rust from forming.

These are just the basic steps; a wealth of information about electrolytic rust removal is available. Do your research before attempting this process so that you fully understand the requirements and risks involved.

Method 6: Sandblasting
Sandblasting is one of the easiest and quickest ways to remove rust, old paint, dirt and grease from metal and other hard surfaces. With the proper abrasive media, this process (sometimes referred to as bead or pressure blasting) can strip years of corrosion from plate steel, yet it can delicately etch glass or carve wood. Sandblasting is a perfect method for restoring intricate metalwork such as wrought iron fencing or for removing layers of paint from nooks and crannies in old cast-iron radiators.

The sandblasting process works on the same principle as a paint sprayer. Compressed air at high pressure blows fine sand or other abrasive material through a hardened-steel, carbide or ceramic spray nozzle. The most common blasting media for removing rust are coal slag (also known as Black Beauty, Black Diamond and Black Blast) and silica sand.

When sandblasting, slowly work back and forth across the workpiece until the particles strip away all traces of rust.

If you want to set up a sandblasting rig, you’ll need an air compressor capable of delivering 70 to 125 psi at 6 cfm or greater, a sandblasting gun and blasting media. Though not a technically demanding process, sandblasting does pose safety hazards (such as silicosis, a life-threatening condition caused by inhaled silica sand that prevents oxygen from entering the bloodstream). Always wear proper safety gear and follow all instructions that are provided with the blasting equipment and media.

Method 7: Removal and replacement
Sometimes rust is impossible to scrape off, convert, dissolve or blast away. In those cases, you’ll need to cut away the ruined metal and replace it with fresh steel (a common practice in automotive restoration). Entire books have been written about this process (especially for automotive hobbyists), and you should research the techniques and practice on scrap metal before cutting into a cherished workpiece.

The first step is cut away the terminally rusted spots until all that’s left is solid metal. Use a wire brush to strip away the paint in the affected areas to make sure that the rust has not migrated beneath the paint into the surrounding metal. Feather the paint at the transition from the damaged area to solid metal so that there are no abrupt surface changes.

Create a patch from new metal that matches the size and contour of the damaged area and weld it into place. Start with a few tack welds to hold the patch in position; then run a bead around the entire patch and grind the welds smooth.

After you’ve finished welding and grinding, apply body filler to help the repaired area blend with the surrounding metal. Apply the filler as smoothly as possible, and follow the manufacturer’s directions, as different types of body fillers have different application requirements. Once the filler dries, sand it smooth with 80-grit sandpaper.

When priming and painting, patience is key. After applying primer, sand the repaired area to smooth the surface and discover any spots that may need additional filler. Remove any sanding dust, apply a second coat of primer, sand and repeat a third time. Then apply a topcoat of your choice, again following the manufacturer’s directions.