Concrete is one of the most durable surfaces used across New Zealand homes and commercial properties — from driveways and patios to garage floors, pathways, carparks, and warehouse slabs. But despite its strength, untreated concrete is highly porous and vulnerable to staining, moisture intrusion, surface breakdown, and premature ageing.
That’s where concrete acid washing and sealing comes in.
In this 2026 guide, we’ll walk through everything property owners need to know about acid washing concrete, why it’s essential before sealing, how the process works, and how professional sealing can dramatically extend the life and appearance of your concrete surfaces.
If you’re considering restoring tired concrete or protecting newly cleaned surfaces, this guide will help you make an informed decision — and avoid costly mistakes.
What Is Concrete Acid Washing?
Concrete acid washing is a specialised surface preparation process that removes deep-set contaminants and opens up the concrete’s pores, allowing sealers to properly bond.
Unlike standard water blasting alone, acid washing works at a chemical level, breaking down mineral deposits and surface residue that pressure alone cannot remove.
What Acid Washing Removes
Concrete acid washing is highly effective at removing:
- Efflorescence (white chalky salt deposits)
- Cement laitance (powdery residue left from curing)
- Rust and metal stains
- Ground-in dirt and traffic grime
- Old sealer residue and patchy coatings
- Construction residue and concrete haze
This process creates a uniform, clean, and receptive surface — which is essential before sealing.
Why Acid Washing Is Essential Before Sealing
One of the biggest mistakes we see is sealing concrete without proper preparation.
Sealers rely on penetrating the concrete surface. If pores are clogged with residue or contaminants, the sealer:
- Won’t bond properly
- May appear patchy or milky
- Can peel or fail prematurely
- Won’t deliver long-term protection
Acid Washing vs Pressure Washing
While pressure washing is important, it’s often not enough on its own.
| Pressure Washing | Acid Washing |
|---|---|
| Removes surface dirt | Removes embedded mineral residue |
| Mechanical cleaning | Chemical deep cleaning |
| Limited pore opening | Actively opens concrete pores |
| Not sufficient for sealing alone | Essential before sealing |
Acid washing ensures the concrete is fully prepared, allowing sealers to absorb evenly and perform as intended.
The Concrete Acid Washing Process (Professional Method)
At Metro Water Blasting, concrete acid washing is carried out using a controlled, professional system — not DIY acids or hardware-store shortcuts.
Step 1: Initial Pressure Cleaning
The surface is thoroughly pressure cleaned to remove loose debris, grime, moss, mould, and surface contaminants.
Step 2: Acid Application
A professional-grade acid solution is applied evenly across the concrete surface. The solution reacts with the surface, breaking down mineral deposits and opening pores.
Step 3: Mechanical Agitation
The acid is worked into the surface using rotary scrubbers or stiff brushes to ensure even coverage and penetration.
Step 4: Neutralisation & Rinse
The surface is fully neutralised and rinsed to prevent ongoing chemical reaction and ensure the concrete is safe and stable before sealing.
Step 5: Drying Period
Concrete must dry completely before sealing. This step is critical — sealing over moisture can cause failure.
What Is Concrete Sealing?
Concrete sealing involves applying a protective barrier that penetrates or coats the surface, protecting it from damage while enhancing appearance.
Sealing transforms raw concrete into a durable, easy-to-maintain surface.
Key Benefits of Concrete Sealing
- Protects against oil, grease, and stains
- Reduces moisture penetration
- Prevents mould, algae, and moss growth
- Enhances colour and appearance
- Reduces surface dusting
- Extends concrete lifespan
- Makes cleaning easier
In short, sealing is what turns cleaned concrete into long-term concrete protection.
Types of Concrete Sealers Used in 2026
Not all sealers are the same. Choosing the correct sealer depends on surface use, exposure, and desired finish.
Penetrating Sealers
- Absorb into concrete pores
- Invisible or natural finish
- Ideal for driveways and outdoor areas
- Excellent moisture and stain resistance
Acrylic Sealers
- Surface-forming protective layer
- Enhance colour and sheen
- Faster drying times
- Suitable for decorative and light-traffic areas
High-Performance Industrial Sealers
- Designed for heavy traffic and commercial use
- High chemical resistance
- Long-term durability
- Ideal for warehouses, carparks, and workshops
Our team selects the correct sealer for each surface, ensuring performance and longevity.
Where Concrete Acid Washing & Sealing Is Most Effective
Concrete acid washing and sealing is ideal for:
Residential Properties
- Driveways
- Patios and courtyards
- Garage floors
- Pathways
- Pool surrounds
- Exposed aggregate
Commercial & Industrial Properties
- Carparks
- Warehouses
- Workshops
- Retail forecourts
- Factory floors
- Shared access lanes
In high-traffic or high-exposure areas, sealing is not optional — it’s essential.
How Long Does Acid Washed & Sealed Concrete Last?
When done correctly:
- Acid washing restores surface integrity
- Professional sealing can last 3–7+ years
- Maintenance cleaning becomes faster and easier
- Surface wear is significantly reduced
Unsealed concrete, by comparison, often begins to stain and degrade within 12–24 months.
Common Mistakes to Avoid
Concrete sealing failures usually come down to poor preparation or rushed processes.
Mistakes We See Often
- Skipping acid washing
- Sealing damp concrete
- Using incorrect sealer types
- DIY acid misuse damaging surfaces
- Applying sealers too thickly
- No neutralisation after acid washing
These mistakes lead to patchiness, peeling, and wasted money.
Why Professional Concrete Acid Washing & Sealing Matters
Concrete restoration is not a DIY job if you want lasting results.
Professional services ensure:
- Correct acid strength and application
- Safe handling and environmental controls
- Proper neutralisation
- Correct drying times
- Even, professional sealer application
- Long-term surface protection
At Metro Water Blasting, we specialise in complete concrete restoration systems, not shortcuts.
Concrete Acid Washing & Sealing for 2026 and Beyond
With increasing property values and rising replacement costs, protecting existing concrete is one of the smartest investments property owners can make in 2026.
Acid washing and sealing:
- Preserves structural integrity
- Improves appearance instantly
- Reduces long-term maintenance costs
- Enhances property presentation
- Extends the usable life of concrete surfaces
It’s restoration, protection, and prevention — all in one process.
Professional Concrete Sealing Services
If you’re considering professional concrete acid washing and sealing, we recommend working with experienced specialists who understand surface preparation, chemistry, and long-term performance.
Learn more about our professional concrete sealing solutions here:
👉 https://www.metrowaterblasting.co.nz/concrete-sealing-services/
Our team services residential, commercial, and industrial concrete surfaces with tailored solutions designed to last.
Ready to Protect Your Concrete?
Whether your concrete needs restoration, protection, or both, professional acid washing and sealing delivers results that water blasting alone cannot.
Request a no-obligation quote today and let our specialists assess the best solution for your concrete surfaces.