by Ron Joseph
Painting Concrete Block
Q. I have concrete block that we used in the construction of our office and
shop building. We have not had much luck with the black paint we have used in
the past. So what I would like to know is what type of paint do you recommend
for painting concrete block?
A. There can be several reasons for the paints inability to adhere well to
the concrete block. Most often concrete or cement will produce an efflorescence
or alkaline salt that is deposited on the surface.
For the coating system to perform properly, these salts must be neutralized
and removed to produce a good clean surface for the paint or coating to adhere
to. This may be accomplished by using a high pressure power washer. In some
instances the alkaline salts are neutralized with a mild acid solution such
as Muriatic Acid. I don't recommend using an acid solution for an application
such as this.
Investigate the availability of various types of concrete coatings from your
local paint dealer. Explain your situation, ask for specific product and application
recommendations. Be certain to discuss the needed prep work.
Remove all loose or flaking paint, I would think that you would have to remove
most if not all of the existing paint from the surface of the block in order
to create a good foundation in which to apply your coating to. Allow the block
surface sufficient time to dry out after washing.
Ask the paint dealer about the use of a primer prior to applying the top coat
paint. More often than not, a primer is necessary to ensure a good sound coating
system that will last for several years.
When preparing any surface for the application of paints or coatings, be certain
to take precautions to protect against breathing in any air borne dust particles
or debris that may be created by the prep work.
Please be aware that paints, coatings and solvents are chemicals and therefore
you should always pay attention to proper handling procedures and be prepared
to wear protective clothing, such as respirators, gloves, coveralls, etc. For
further information on the health and safety requirements for the coatings and
solvents you wish to use we strongly advised you to contact your local coating
supplier. If possible, go the extra step and look for this information on the
website of the product vendor.
Proper handling and care must always be used when using
any corrosive products. YOU MUST insure that you are properly protected
with goggles, breathing protection, acid-resistant gloves and the proper clothing
so that you don't injure yourself. Be certain to provide plenty of fresh
For similar reasons, please insure that you keep others
away from this process, Especially children. Acid is always diluted before use.
The typical dilution for most applications
is one part Muriatic Acid Slowly and Carefully added to ten parts water.
Always add the acid to the water! Never add the water to the Acid! Gently
stir the water while adding the acid. Be careful when mixing to avoid splashing
the acid. Do not mix in a paper, ceramic, or metal bucket... use Acid resistant
mixing containers such as glass or plastic.
We urge you to visit the web sites listed below for further information on
the proper handling, use and disposal of Muriatic Acid.