F. Mechanical Prep vs. Acid Etching
Resinous flooring materials ideally bond to concrete with a rough, sand-paper finish.This finish can be achieved by either acid etching or mechanical methods. The choice of preparation is dictated by the factors above. Other factors which determine the type of preparation include:
1. Ecological restrictions involved with waste removal which could prohibit the use of acid etching and other chemical methods.
2. The type of resinous flooring material: It is recommended that concrete floors be acid etched prior to application of polyester and vinyl ester flooring systems.
G. Acid Etching
The following steps are recommended for acid etching:
1. Dilute commercial muriatic acid with water using 1 part acid by volume to 3 parts clean water by volume. Add the acid slowly taking care to avoid splashing. Workers should be protected with safety glasses, rubber gloves, and boots. If skin or eye contact occurs, rinse affected area thoroughly with clean water and follow Material Safety Data recommendations.
2. Sprinkle acid solution onto the entire surface in order to allow the acid to reach all areas of the concrete. Adequate coverage is approximately 75 ft²/gallon of acid/water solution. Do not puddle and spread.
3. Scrub the acid solution into the concrete using a stiff bristle broom to remove loose concrete and laitancy.
4. Before rinsing, look for areas where bubbling did not occur. These areas have not been sufficiently cleaned and will require mechanical scarifying and additional acid etching.
5. When the acid solution has stopped bubbling (usually after approximately 15 minutes), rinse the floor thoroughly with water. Do not allow the floor to dry before rinsing because the salts formed by the acid reaction may cause problems with the adhesion and performance of the resinous flooring system. Test pH of the concrete surface to verify that the concrete tests alkaline.
6. Finally, the floor should be dry mopped to remove standing water and dirt remaining after the acid etching. Allow the floor to completely dry prior to the application of any resinous flooring system. Failures can occur in resinous flooring system applications due to moisture remaining in the substrate.
H. Mechanical Preparation
Contamination and other foreign materials must be mechanically removed to ensure a satisfactory bond. All dust and debris must be thoroughly removed.