Essential preparation before painting
If you are painting a bare concrete floor, it is essential that the surface is prepared to prevent the paint peeling. New concrete often has a weak dusty layer of cement deposits which would have risen to the surface as the concrete dried. Old bare concrete will have loose cement and grit embedded in the surface. Etching the floor addresses both these problems. If it is not done, the paint will just stick to the loose surface material and will break away with the weak deposits on the underside of the paint as the floor is put into use.
Most paints rely on a degree of penetration into bare concrete and etching will help open up hard, smooth concrete (not power floated, please see Watco Powerfloat Primer), to allow the paint to penetrate and key. Dirt, dust and light oil is also removed by etching. Following etching the concrete will be ‘brighter and whiter’ and look like it is ready for painting.
| Suitable for | Bare concrete new and old |
| Composition | Dilute hydrochloric acid solution |
| Coverage | 20m² per 5L |
| Recommended number of coats | 1 |
| Storage | Do not allow to freeze. |
| Shelf life | 24 months in unopened containers. |
Remove any heavy oil and grease using Watco Bio D.
If the floor is reasonably clean, just give it a sweep to remove dust.
The concrete floor should be dry before using the Acid Etcher.
Tip the 5L unit into a plastic watering can fitted with a rose and apply evenly to an area not exceeding 20m².
Scrub with a stiff broom. The Acid Etcher will froth as it reacts with the alkaline concrete.
When the frothing stops it means the Acid Etcher has done its job. It will have loosened the weak surface material. This will need washing off.
Use clean water and a broom to wash the reacted Acid Etcher away. The acid will be neutralised by now and will not be harmful.
Allow the floor to dry. It is then ready for painting.
