The acid washing of concrete is a requirement after the concrete has cured sufficiently, in order to remove surface efflorescence and to open the pores before sealing. This will help the sealer to penetrate and result in a superior bond between the sealer and the surface.
Scrub the acid solution: Once the solution is applied, lightly scrub it into the concrete with a push broom or long handled scrub brush. This helps to create a uniform etch of the concrete. Let the solution sit from 2 – 15 minutes while it continues to fizz and bubble.
In most cases, special cleaning and/or etching of the concrete surface will be required before painting, and the appropriate cleaner (often TSP, trisodium phosphate) and etcher (usually a solution of muriatic acid) can be obtained. These chemicals, especially the etcher, must be used with care.
Acid stains penetrate the porous concrete through a chemical reaction. The acid in the stain reacts with the concrete lime and inorganic metal salts. This chemical reaction creates a permanent color change.
The concrete must be 28 days old or at least have cured to one uniform color prior to acid staining.
They may be used on everything from concrete floors and kitchen counters to pool decks and driveways, both inside and out. So in saying that acid stain can last 5 to 20 years depending on many factors.
Without proper surface prep, you could end up with a coating that flakes or rubs off much sooner than it should. One of the main reasons for needing to know how to etch a concrete floor for painting is because of laitance.
So while you don't have to seal concrete, if you do, you will be enhancing and protecting the look of the concrete while extending it's lifespan considerably.
Concrete isn't usually a good substrate for holding coatings because of its high porosity and alkalinity. “Without it (bonding primer), there's nothing for the coating to grab onto,” says Pachade. If the concrete substrate is not primed, “You'll see pinholes because the concrete is breathing.”
Over time, it can destroy concrete as the acid weakens its structure. This will cause scaling, pitting, peeling, and cracking. If the acid wash gets into the soil, it will evaporate on the surface but remain beneath the surface (just like it does with concrete).
One of the most common methods of removing stubborn dirt and stains on outdoor concrete floors is by using muriatic acid. Muriatic acid is one of the most common substances when it comes to household cleaning and disinfection.
Cleaning concrete with muriatic acid can be a highly effective solution if used correctly, providing ultra-bright white concrete and removal of many types of stains. In one application, you can remove rust stains, oil stains, algae, and paint splatter with a quick chemical application followed by pressure washing.
concrete can deteriorate. Freezing of trapped water, the effects of sea water, even certain bacteria and fungi can damage it. Particularly damaging to concrete are acids.
Concrete Cleaning and Sealing: DIY vs.
DIY is certainly the cheaper option; homeowners will typically spend between $0.20 and $0.75 per square foot when cleaning and sealing concrete themselves, whereas that cost increases to between $1.20 and $1.75 per square foot when left to a professional.
Any concrete that is not properly neutralized will begin decomposing immediately. It may take time for the damage to reach the surface where you can see it, but it is happening and is usually irrepairable.
Though new concrete may not always require a second coat of acid stain, older concrete does require two coats of stain for complete coverage. For a more diffuse look, spray the stain onto the surface without brushing.
The cost to install acid stains is around $2 to $6 per square foot for basic designs or $12 to $25 per square foot for complex colors and patterns. Acid stains, also called reactive stains, contain hydrochloric acid and metallic salts that chemically react with concrete to produce earthy colors.
One of the very best sealers on the market today for acid-stained concrete and other types of decorative concrete flooring is the "polyurea". Polyurea is extremely durable, long-lasting and easy to maintain. Most clear sealers for concrete come in water and solvent-based versions.
Safer Alternatives to Acid Etching Concrete
The best alternative to prepping a concrete slab for an epoxy coating application is called mechanical grinding. Concrete grinding is when you utilize concrete equipment that is equipped with grinding tools (or discs) to remove the smooth top layer of a concrete slab.
For the best performance from a coating system, concrete must be clean and have a uniform open/porous surface before application. The surface must be etched until this is achieved. More than one etch may be required. The next steps include patching any holes or cracks before applying the epoxy.
Natural Stone Countertops. Granite, marble and concrete are porous. Spraying these surfaces with vinegar can cause etching and loss of shine.
Acid-Based Stains
An acid-based stain costs between $0.20 and $0.40 per square foot on average or a total of $2 to $14.50 per square foot with labor. Acid-based stains chemically react with your concrete flooring, giving a natural appearance.
Acid-stained concrete is durable and resistant to UV light, moisture, and damage. The environmentally friendly finish also creates a beautifully stained surface that costs next to nothing after initial installation.
To help prevent this, it's a good idea to slightly dampen the surface of the concrete before applying the acid stain. This will help ensure that the stain has enough moisture to react properly with the concrete.