Priming concrete is the all-important step number three of a concrete painting job – right behind cleaning thoroughly to remove dirt and efflorescence (the white powder often found on damp concrete) and applying a sealer to inhibit moisture damage, and just before the final step of painting.
For both exterior and interior projects, applying a specially formulated primer to concrete prepares the surface, accomplishing several important and beneficial environments:
- Primer fills any small gaps or voids, creating a smooth, uniform surface
- Primer works as a bonding agent between the concrete and the paint, assuring proper adhesion to both surfaces
- Primer soaks into cement, protecting it from damage over time
- Primer prolongs the life of the paint or stain
- Primer turns a poor surface for paint into one that accepts paint and topcoats beautifully
How do you know if a concrete surface needs a primer? Generally speaking, priming is so essential to successful painting outcomes, concrete will always needs a primer. However, the existing surface needs to be primed before painting if:
- It is unpainted
- It is peeling
- It is chipping
- It is chalking
- It is incompatible with the type of paint being used
Types of Concrete Primers
Primers are formulated in three ways: alkyd/oil base, acrylic/latex and tinted shellac, and are specialized for both exterior and interior applications. If you are working on a tight budget and have a variety of surfaces that need to be primed, a universal primer is formulated to work on almost any surface. Nowadays though, contractors want to ensure a successful concrete painting job with primer made specifically for concrete.
For example, the type of primer specified for use with LevelFlor® Rapid Set, a cement-based, self-leveling underlayment (SLU) that can be used both indoors and out, is Rapid Set® Acrylic Primer or Rapid Set TRU Epoxy Primer (TXP). These products are specially formulated to seal the LevelFlor layer, reducing the number of pinholes or bubbles caused by trapped air that can mitigate the surface, reducing water loss and increasing topcoat adhesion.
Acrylic/Latex: Because concrete is porous, a water-based or acrylic primer is more likely to soak into the concrete than an oil-based primer, bonding to the substrate and allowing the paint to grip the surface. These primers will also reduce the dust on interior concrete.
Polyurethane/Epoxy: A type of acrylic/latex primer, these products are not only incredibly strong and heavy-duty, they can be made to resist chemical attack and other nasty work environments in commercial or industrial work areas.
Acrylic Masonry: Specifically designed to protect against lime burn, discoloration and efflorescence, masonry primers are used on properly cured, unpainted or new concrete. These are great for outdoor applications, too.
Acrylic Block Fill: If you’re working with cinder blocks, this primer is specially formulated for new or unpainted, smooth or split face concrete blocks.