Step By Step Instructions Of Acid Etching Concrete
Concrete is a surface that can be too hard and smooth to accept paint or protective sealants if in case you have not treated it in any way after being poured. However, etching the concrete with the help of an acid opens the pores of the concrete as well as gets the surface ready in order to accept its next treatment. It is also highly possible to get the concrete ready manually by scraping or wearing it away with the help of a grinder, acid etching is typically much less labor-intensive. In order to acid etch the concrete surface, go through the below-mentioned steps carefully:
- Properly Clean Concrete Surface: Firstly, you need to free the concrete surface from all the dirt, dust, grease, oils, wax, release agents, or any other impurities that will come in the way of the acid etching process. Mechanical cleaning with the help of stiff bristle brushes or machine will be needed for cleaners in order to work properly. Some impurities may not be eliminated by cleaning and will need the surface layer of the concrete to be removed by mechanical means, including shot blasting, sanding, grinding, etc.
- Properly Mix Acid Solution: Some of the acids used for the process of etching the concrete include muriatic, sulfuric, phosphoric, or citric acids, mostly used are muriatic and phosphoric acids. Only plastic or acid-resistant containers need to be used in order to mix and apply the acid. Acid concentrations can be different for different acids, therefore, in order to ascertain or establish the strength and concentration to use for etching the concrete, examine with a very dilute solution then add acid to the container as long as the strong bubbling action is noted in the examination. Allow near about 50 – 75 sq ft for rough concrete and 75 – 100 sq ft for smooth concrete.
- Wet-out Concrete Surface: Now, wet-out the concrete surface with the help of fresh, clean, uncontaminated water in order to make sure that the concrete is uniformly wet, without any standing or ponding water. The concrete must stay wet as long as the acid solution is applied.
- Apply Acid Solution Uniformly: Apply acid solution evenly & consistently over the wet surface of the concrete. The use of plastic watering can help you to apply fresh acid evenly over the concrete surface. If you have applied the acid properly to a clean surface, it will start to bubble giving indications that the acid is reacting with the concrete. If in case the acid fails to bubble, it means that the surface wasn’t cleaned rigorously enough and must be cleaned as well as etched once again. With the help of a stiff bristle brush, scrub the acid into the surface and get rid of the layer of concrete in order to create the profile needed to apply the coating system.
- Allow 2–10 Minutes Acid Time To React: Allow the acid to stay on the surface of the concrete as long as the bubbling stops, generally betwixt 2 – 10 minutes. Make sure not to allow any parts of the etched surface to dry out during this time.
- Rinse/scrub Surface: As soon as the bubbling of the acid slows noticeably, flush the concrete rigorously with plenty of water while scrubbing the surface with the help of stiff bristle brooms in order to get rid of the powdery residue from the porous of the concrete. Continue this process as long as the concrete is rinsed properly. Collect as well as dispose of the liquids as per the local and national regulations. As soon as the floor is dry, any powdery residue that stays on the concrete must be eliminated & then apply the coating system.
- Check Profile: The profile of the concrete surface should be betwixt 80 – 120 grit open coat aluminum oxide sandpaper. The concrete must have an even & consistent open/porous surface before applying the coating system. The surface must be etched as long as this is achieved & for this you may need more than one etch.
- Check The PH: The perfect pH value is 7.0, but 7.0-8.5 is acceptable. Neutralize the surface if needed. After the final rinse, check the pH value of the wet surface. The perfect pH is 7.0 (neutral) but a pH of 7.0-8.5 is also acceptable for most coatings without the provision that otherwise specified. If in case the pH is below 7.0, residual acid on the concrete surface must be counterbalanced. One cup of household ammonia per gal of fresh water will generally counterbalance the concrete in one application. Apply solution evenly & consistently over the surface & keep it as it is for 10 minutes before flushing and scrubbing with distilled water. Again check the pH and continue the process if the pH is below 7.0. Use indicators like pH strips, pH pencils, or Phenolphthalein solution. As soon as you have reached your desired results, the floor should be completely dry before applying the coating system.
Warnings:
- Acid etching needs the use of strong chemicals. Improper use of these chemicals can lead to severe injury. At the time of handling harmful chemicals, make sure to use protective clothing, protective eyewear/face shield, rubber gloves, and boots & also take care not to breathe vapors.
- Always add acid to water, & avoid adding water to acid.
- Protect the concrete surfaces that you are planning not to etch from chemical vapors, splash, and spills.