How Does pH Affect Polymer Coatings Ability to Adhere?
Thermal-Chem believes that when applying our products, you should have as much information as possible about the concrete you are about to coat.
Let’s talk about pH and how easy it is to test, and the failures that can occur on a slab of concrete that is not within the normal standards.
pH (power of hydrogen) is a scale that is used to measure how basic or acidic a water-based solution is. This scale ranges from 0-14. If a solution has a pH less than 7, it is considered acidic. If a solution has a pH greater than 7, it is considered basic or alkaline. A pH level of 7 is considered neutral. For example, water has a pH of 7.
The ideal pH level of a concrete substrate, whether too high or too low, will affect the overall adhesion or bond strength. The ideal pH value for applying polymer systems such as those manufactured by Thermal-Chem is 7, although 6.5-8 is acceptable. See the scale above.
Testing a concrete substrate is quite easy. You will need a bottle of water (tap water may alter the results), and a litmus pH strip.
- Clean the concrete to be free of dirt, dust, or anything preventing the substrate from being porous.
- Pour a puddle of water 1”-2”, and allow to stand for at least one minute.
- Place the pH strip into the water and remove immediately.
- Compare the color of the pH strip with the above color chart to determine the pH.
Dealing with abnormal readings. Fresh concrete will typically test between 10-12, so make sure you are not dealing with a new piece of concrete. Additionally, if you have already prepared your concrete either by diamond grinding or shot-blasting this, will also cause high readings. If either of these are not factors to consider, remediating concrete to a neutral reading is not difficult. Usually, a neutralizing detergent applied to the concrete and then rinsed will bring down elevated readings. Highly acidic surfaces can be neutralized by using a diluted solution of caustic soda or baking soda. Let this sit on the concrete for 10-15 minutes then rinse at least twice.
Don’t let a project fail because of a lack of performing a 10-minute test. Be a true professional and know your project. Contact Thermal-Chem for more information about our products and to help make your next concrete flooring project a success.