Professional Methods To Remove Tough Rust Stains from Concrete: Step-by-Step Guide

Rust stains on concrete can be an unsightly issue for both indoor and outdoor concrete surfaces and are a result of many different factors. The good news is that most concrete rust stains are not permanent!

In this blog, we're sharing a couple of methods for removing rust stains from concrete using a combination of the right cleaners, chemicals, tools, and techniques.

How Rust Stains On Concrete Happen

While it can sometimes be difficult to determine how rust stains came to be on a concrete surface, there are a handful of common causes that can help you pinpoint the source of staining - so you can advise clients on how best to prevent them in the future:

• The presence of iron in the concrete mixture: Concrete mixtures commonly contain small amounts of iron due to impurities in sand or gravel. When this iron oxidizes (rusts), it can cause surface stains that are brownish-orange in color.
• Rebar corrosion: Mostconcrete structures have steel reinforcement bars (rebar) inside that help them maintain their structural integrity. If the concrete cracks or becomes porous, water can infiltrate the concrete and come into contact with the internal rebar, which can lead to rust formation that leaches out and stains the concrete surface.
• Metal objects on concrete: Metal objects like tools, furniture or vehicles that are left out in the rain and condensation or otherwise begin to rust while sitting atop concrete can cause surface staining when they crumble away or leak onto the surface below.
• Fertilizers and lawn chemicals: Granular fertilizer may contain iron. If used near concrete, it can cause rust stains once it encounters moisture - whether from rain or a lawn sprinkler.
• Water sources with high iron content: Water with high iron content, such as well water, can cause rust stains on concrete, particularly when it's used for irrigation or cleaning.

Preparing To Clean Rust From Concrete

Before you get started with the concrete rust stain removal process, there are a few important details to keep in mind:

• Determine the extent and depth of the rust stain: Depending on how ingrained the rust stain is, you'll need to choose an appropriate rust remover. For example, if the culprit of the staining is corroded rebar, it likely goes deep below the surface. If caused by metal objects set on top of the concrete, a less harsh rust remover should do the trick.
• Use personal protective equipment: Rust removal products can be harmful to your skin, eyes and lungs. Wear gloves, safety goggles and a mask to protect against chemical exposure.
• Ventile the area: Ensure the area is well-ventilated if working indoors to prevent inhalation of harmful chemicals.
• Remove surface debris: To prepare the surface, sweep or use a pressure washer to remove dirt and debris. This allows the cleaning agent to penetrate the stubborn rust stain more effectively.

How To Remove Rust From Concrete: Two Commercial Cleaners That Do the Trick

Once you're prepped and ready, choose a powerful commercial concrete rust stain remover, such as Prosoco Consolideck Concrete Floor Restorer for minor rust stains or Prosoco Sure Klean Ferrous Stain Remover for heavier staining and other metallic discolorations.

Something to keep in mind before you begin: If spot-treating stained areas, expect a lightening in the color of the concrete itself compared to areas not treated. Although these are the best-known rust-removing chemicals in the industry, less pronounced discoloration may remain where the original stain appeared. This can be more extreme when treating older or dirtier slabs.

Product #1: Prosoco Consolideck Concrete Floor Restorer

Before beginning, test for proper dilution. Start with 1 part cleaner to 6 parts fresh water. Do not exceed 1 part cleaner to 3 parts fresh water. Use the mildest dilution that produces results and always pour cold water into an empty bucket first, then carefully add the cleaner. Never use hot water. Handle in plastic buckets only. Acidic materials and fumes attack metal.

1. Apply cleaner evenly to a dry surface with an acid-resistant mop, applicator or low-pressure spray.
2. Let the cleaner dwell on the surface for 3-5 minutes or until the stains dissolve. If treated surfaces are left unattended, keep people away from the cleaner. Scrubbing with an acid-resistant, stiff brush may improve results. Note: Do not let the cleaner dry on the surface. If it starts to dry, lightly wet the treated surface with fresh water, reapply the cleaner and scrub gently.
3. Rinse thoroughly with fresh water to get all residues off the surface. If pressure-rinsing equipment is not available, brush the surface while rinsing with plenty of clean water.

Product #2: Prosoco Sure Klean Ferrous Stain Remover

Always test a small area (minimum 4 ft x 4 ft) of each surface to confirm suitability and desired results before beginning the overall application. Test each type of masonry and each type of stain. Test with the same equipment, recommended surface preparation and application procedures planned for general application. Let the test area dry for 3-7 days before inspection and approval. Make the test panel available for comparison throughout the cleaning project.

Ferrous Stain Remover can be diluted with up to 3 parts fresh water or applied in concentrate, depending on test results. Always pour cold water into an empty bucket first, then carefully add the product. Never use hot water. Handle in polypropylene buckets only. Acidic materials and fumes attack metal.

1. Working from the bottom to the top, always prewet the masonry surface with clean water.
2. Apply prepared cleaner directly to the masonry surface.
3. Let the cleaner dwell on the surface for 3-5 minutes. Note: Do not let it dry into the masonry between applications or before the final rinse. If treated surfaces are left unattended, keep people away from the cleaner.
4. Reapply cleaner and rinse with fresh water from the bottom to the top. Thorough rinsing is important to get all residues off the surface. If pressure rinsing equipment is not available, rinse thoroughly with clean water. Use a scrub brush while rinsing.

For more information or to place an order, please contact a Jon-Don Concrete Expert at 800-556-6366.

Make Concrete Look New Again After Stain Removal

After successful rust removal, concrete may require extra care and refinishing. Explore our library of tech tips that teach you how to tackle a variety of concrete-related cleaning, restoration, maintenance, and more!

Need to brush up on your concrete polishing skills? Check out our hands-on, 2-day course to learn everything from identifying concrete types to using diamond tooling and performing basic repairs.