By Rob Robillard
Remove Rust Spots from Asphalt
It’s easy to know the right thing to do after you’ve made a mistake.
A few months back, I was cutting a bunch of metal rods (rebar) and did not anticipate all the microscopic metal dust remaining on my driveway and leaving unsightly rust stains.
My first thought was to pressure-wash the driveway. However, rust comes from a chemical reaction and pressure-washing is typically not enough to remove it.
Instead, I spot-treated the rust spots with an acid-based stain remover.
I’ve used ZEP’s Calcium, Lime Scale, and Rust remover (called ZEP CLR for short) on a few remodeling projects in the past, as when salvaging claw-foot tubs with heavy mineral staining, and the product worked amazingly well. ZEP is a time-tested, professional-grade cleaner that’s been around for 80 years.
To begin, use the CLR remover on a small, inconspicuous spot to test it before using on the entire stained area. It needs to be rinsed off quickly, so keep a hose handy.
Mixing the CLR Solution
The ZEP Calcium, Lime Scale, and Rust remover is a fast-acting, concentrated cleaner. Here’s the best approach to using it for rust stains on a driveway:
- Mix a 50/50 solution using warm water.
- Apply to stained surfaces with a stiff-bristle brush.
- Rinse after 5–10 minutes.
- Perform a second application at full strength, if needed.
- Rinse again.
- It’s important to always read the manufacturer’s label and follow their instructions.
Pressure-wash the Driveway
Once the rust stain was treated, I used Zep Driveway and Concrete Pressure Wash Cleaner Concentrate in my pressure washer to clean the entire driveway surface.
I simply add this cleaner to my pressure washer’s detergent reservoir and I’m good to go. As both a remodeling contractor and a homeowner, I like construction-grade, concentrated cleaners like this, because there’s no futzing around, I simply add the cleaner to the pressure washer and get the job done fast.
The Zep Pressure Wash Cleaner is designed to remove tough oil stains and grime from asphalt, brick, concrete or other aggregate surfaces. (It is not intended for painted or wood surfaces that will not be refinished.)
- Wet all surrounding vegetation and grass with pure water. Saturate the soil to avoid plants from soaking up chemical overspray. (You can also cover plants with plastic if desired.)
- Most driveways have a slope, so you should work on the uphill side of the slope.
- Apply the cleaner to the driveway at low pressure, working in manageable sections.
- Keep the surface wet, re-applying the cleaner as needed.
- Allow the cleaner to soak in for 5-10 minutes.
- Pressure-wash the surface in sections, working in a down-slope direction.
Pro Tip: The Zep Driveway and Concrete Pressure Wash Cleaner requires you to use a pressure washer with a downstream chemical injector. Downstream injection introduces the chemical into the system after the pump, so no chemical will be run through the pressure-washer pump.
Like I said earlier, a little foresight may have prevented the need to do this project, but that’s life. Stuff happens, and we have to deal with it. The key is to use the right tools to get the job done safely, efficiently and effectively.
By following these steps using a pressure washer and a well-known, pro-grade cleaner, you’ll be well on your way to a clean driveway, walkway or patio.
Editor’s Note: Rob Robillard is a professional remodeling contractor. Visit his website at www.aconcordcarpenter.com.