Do you want to acid wash concrete patio in the summer for coating, but don’t know how to acid wash concrete? Or maybe you have heard of acid washing, but don’t know what it is exactly and how it is done?
You don’t have to look any further as here is one simple tutorial for doing it and an explanation of the process. It’s good to make it clear that it’s not about acid staining as acid washing can be harmful to that.
Acid washing vs acid staining
Acid washing and acid staining, although often used interchangeably, are two entirely different processes used for different purposes. While staining involves the actual coloration of the concrete flooring or slab, acid washing is the process that prepares the pores in the concrete for accepting other coatings.
Why is it harmful for acid staining? When you acid stain the concrete, the acid reacts with the minerals in the concrete. If you have acid washed the concrete, there is less minerals to react with right? This is why it’s not recommended to do these two together.
With that said, let us take a look at how to acid wash concrete in preparation for the staining process.
Acid washing of concrete involves roughing up the surface of the concrete so that the concrete itself will be able to absorb the acid stain in a later process. The actual wash solution does not usually leave any coloring unless you allow the wash to dry on the concrete.
In this case, it may leave behind a white residue that is very difficult to remove. For this reason, it is important to keep your wash solution wet on the concrete; do not let it dry at any time during the procedure.
Allowing the wash to dry can also cause a weakening in the adhesion bonds of the stain to the concrete.
Acid washing can also be used on the concrete for it to be better for adhering to other things as well like resurfacing, painting and coating. There is a layer of “cream” on the surface of the concrete after it has been poured and finished that is not the best surface to apply anything on.
With acid washing, we can open up those pores a bit and make it better for anything that we want to apply to it.
With these warnings well attended to, we can now proceed on to the actual process of how to acid wash concrete flooring.
Steps to acid washing concrete
The entire process usually takes two individuals to accomplish the goal; one person will be wielding the machine that roughens up the floor, and the other will be applying the wash, employing the distribution broom, and handling the rinsing hose.
Step 1: Like most of the time when it comes to working with concrete, the first thing you need to do is prepare the surface. Remove dirt and oil stains from the concrete, here are some tips on how to work with different stains; mold and moss are here and rust and tar are here.
After that, protect other surfaces with plastic so that the acid won’t cause any harm. Tape the plastic into the walls and use other means as well as weights and such.
Step 2: Before you start with acid, pick up proper safety equipment like gloves, boots, a breathing mask, and whatever else you think you might need. You don’t want to get it on your skin or eyes.
Acid is generally harmful so inhaling it or getting it on your skin is harmful and can cause permanent damage. That is why we work carefully with things like this.
Step 3: Now it’s time to pick up our acid. There are some choices like muriatic acid and sulfamic acid, you should check what is available at your local stores.
Once you have figured out the needed strength of your solution from the manufacturer label, pour into your dispensing can and sprinkle evenly over the entire floor.
Hold your dispensing can close to the floor so as to prevent splashing of the wash onto other surfaces.
Note: The solution can cause unsightly and irreparable damage to aluminum and painted metal surfaces. Be careful, too, to keep the wash only on the parts that are to be stained.
Step 4: First you water the concrete before adding the wash solution. After your wash solution has been laid down, use your floor machine or brush to scrub the wash into the floor’s pores.
While the person operating the machine is doing this, the second person should go around with a wire brush or a stiff broom and scrub the areas that the machine cannot reach. If there is no machine, co-op with the brushing and watering.
In addition, that second person will also ensure that the entire surface stays wet while the wash is on it. Once you have completed the scrubbing, rinse well.
You will know that the floor is properly washed when it feels like 80-100 grit sandpaper. If it does not, you must repeat the entire wash/rinse procedure until it does.
Step 5: After the rinse of the final wash pass, you will need to neutralize the reaction by sprinkling a neutralizing solution over the area and aggressively scrubbing again. Now you may rinse for the final time to get the concrete fully clean.
There are also DIY neutralization mixes with water and baking soda as main ingredients or ammonia and water. Personally, I haven’t used them so I can’t provide a proper mixture.
Anyway you need to neutralize the acid so it won’t cause any damage to the concrete or surface that will be applied.
Acid washing is quite a simple job, just remember to protect everything that is not supposed to be washed like metal parts and nature. Also, remember to protect yourself from it.
Whenever we do something like this, be it acid washing or floor grinding, we are careful that our job doesn’t create more work for us. Corroding metal parts would be just like that or ruining surfaces that we’re not working on.
Once your concrete pad, driveway, or flooring is properly acid-washed, rinsed, and dried, it is ready to receive the stain that will begin a marvelous transformation or paint or coating if that’s what you’re after.
Not only floors, acid washing can be used on the house foundation, for example, if you want to do something for the surface. It’s not unusual that it’s just left like that after pouring and to further decorate it, it needs to be roughened up.
Whatever the surface will be and whatever the next layer is, once washed with acid you have a good surface to work on.