Acid etching of concrete
Acid etching will remove the weak, milky layer of cement dust, lime and sand fines that can rise to the surface with over-wet concrete, poor curing or over-trowelling. It involves allowing the reaction of a diluted solution of hydrochloric acid to the concrete surface, then rinsing off with water. The acid will chemically react with the surface, and will dissolve it, allowing it and other water-soluble contaminants to be washed away. By removing the top layer, coatings can firmly adhere to sound concrete giving much longer service life.