Concrete stains are among the toughest challenges in pressure washing. From oil and grease to rust and paint, each stain type requires a different chemical approach. This guide covers what actually works—and what will waste your time and money.
Oil and Grease Stains on Concrete
Fresh oil stains can be absorbed with kitty litter or sawdust, then treated with degreaser. For set-in stains, apply a commercial degreaser (sodium hydroxide or citrus-based) at full strength, scrub with a stiff brush, then pressure wash at 2500-3000 PSI with a 25-degree nozzle. Hot water pressure washers achieve 40% better oil removal than cold water.
Best Degreasers for Concrete
- Sodium hydroxide (NaOH) – most aggressive
- Citrus degreasers – eco-friendly, effective
- Butyl degreasers – commercial grade
- Purple Power or Zep Driveway cleaner
Rust Stains on Concrete
Rust requires oxalic acid or phosphoric acid treatment. Never use bleach on rust—it sets the stain permanently. Apply oxalic acid solution (1 lb per gallon), let dwell 15-20 minutes, scrub, then rinse. For severe stains, F9 BARC (Brick, Algae, Rust, Concrete) is the gold standard professional product.
Step-by-Step Concrete Stain Removal
- Identify the stain type before choosing chemicals
- Pre-wet the surface with water
- Apply appropriate cleaner, dwell 10-20 mins
- Agitate with stiff brush
- Pressure wash at 2500-3500 PSI
- Rinse thoroughly from edges inward
Pro Tips
- Test cleaners in hidden area first
- Work in cooler temperatures when possible
- Never mix acid and bleach products
- Apply a concrete sealer after cleaning to prevent future staining
Frequently Asked Questions
Can pressure washing remove all concrete stains?
Not all stains can be removed with pressure alone. Chemical pre-treatment is essential for oil, rust, and paint stains.
What PSI is best for cleaning concrete?
2500-3500 PSI with a 25-degree nozzle works well for most concrete. Surface cleaners give more uniform results.
How do I remove paint from concrete?
Use a chemical paint stripper first, then pressure wash at 3000+ PSI. Multiple passes may be needed.
Will bleach remove oil stains from concrete?
No. Bleach is ineffective on oil. Use degreasers (alkaline cleaners) instead.
How long should I let cleaner dwell on concrete?
Most degreasers need 5-15 minutes. Rust removers need 15-20 minutes. Never let cleaners dry on the surface.
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