How to Mix Your Own Chemicals to Remove Rust From Tools

Cola contains phosphoric and carbonic acids.

Phosphoric acid is a commonly used chemical for rust removal. You may know it as an ingredient of cola to give it a tangy flavor. Phosphoric acid has the useful property of reacting with rust much faster than it etches (erodes) underlying iron. In addition, the fine, blue-black coating of iron phosphate that it leaves behind prevents rusting. Removing it leaves a bright, hard metal finish that is ready for protective priming to protect against rust recurrence. This can be used to remove rust from and protect your tools.

Things You'll Need

• Phosphoric acid, 85 percent concentration
• Gloves
• Safety glasses
• Distilled water
• Steel wool
• Spray bottle
• Paper towels
• Nonmetal brush
• Baking soda
• Water
• Rusted tool

Instructions

Mix

1. Use enough 85 percent phosphoric acid to submerge the tool. You can buy the acid at hardware or local chemical supply stores or online. Although cola contains phosphoric acid, the concentration is low and might react with the metal by the time it takes to fully react with the rust.

2. Put on gloves and safety glasses.

3. Pour the acid into a glass container as a first choice. Second choice would be a plastic container. This is safe since, after all, this is what cola comes in.

4. Add enough distilled water to water the acid down to 85 percent concentration, if necessary.

5. Store the original container of phosphoric acid afterward consistent with the safety instructions on its label.

Application

1. Clean the tool's surface free of rust with a wire wheel or steel wool and then with soap and water.

2. Dunk the tool into a container of the acid, letting it soak for a few minutes. If the tool won't fit into a container or too much acid would be needed to submerge the tool, pour the phosphoric acid into a spray bottle and soak the rusty part. Alternatively for tools that can't be submersed is to lay paper towels soaked with acid on the rusty tool.

3. Take off the towels or pull the tool out of the solution after a maximum of 15 minutes.

4. Brush the rust off with a nonmetal brush.

5. Rinse the tool with water and repeat the phosphoric acid application if there is rust left.

6. Neutralize any acid remaining on the tool with a solution of baking soda and water. The concentration of the baking soda solution is not as important as continually adding the solution until the acid is fully neutralized and additional baking soda doesn't react.

7. Neutralize any paper towels you may have soaked with acid, using the baking soda solution before throwing them out in the regular trash.

8. Dry the tool with a towel. Drive out remaining moisture using heat, for example from a hair dryer.

9. Prime and paint the iron, if you like. A quick application would provide longer-lasting protection than the thin layer of iron phosphate left behind.

Tips & Warnings

• Do your work in a well-ventilated area.

• Some people conclude that since phosphoric acid is acidic, that a stronger acid would do an even better job at removing rust---an acid like hydrochloric (muriatic) acid. Muriatic and phosphoric acid react with iron in different ways.

• Don't use muriatic acid on cast iron. Pitting results.

References

• A Primer on Rust
• Fooducate: Phosphoric Acid
• Tradekey: 85 Percent Phosphoric Acid

Resources

• VIDEO: Coca Cola Removes Rust
• Alibaba: 85 Percent Phosphoric Acid