What Are the Reasons for Concrete Sealer Failure?

There are several reasons for concrete sealer failure which results in peeling, flaking, or discoloration. This is definitely something you want to avoid because removing sealer can be a huge hassle and a messy job.

• Cheap sealer
  I'm a firm believer in "you get what you pay for". If you pay bottom dollar for a product, then you're going to get a product with poor quality. Avoid sealers that are sold at home improvement stores because they just don't perform vey well and you risk significant discoloration. I recommend contractor supply stores and make sure the label says "non-yellowing". You'll pay a little more but it's well worth it.
  
  
• Other chemicals or foreign substances not completely removed before application
  This is the biggest cause of concrete sealer failure. Anything, whether it's cleaners, dirt, oil, etc., that doesn't get removed from the surface will prevent good bonding between the sealer and the concrete resulting in peeling or flaking. Always test the surface by wetting it and looking for water beading as this is an indication that more cleaning or rinsing needs to be done.
  
  
• Sealer applied before concrete dries completely
  Moisture also prevents good bonding resulting in flaking. Sealing over moist concrete can also cause cloudy or discolored spots. Make sure concrete is completely dry before application. This does not apply to using a "cure and seal" on fresh concrete. Once the concrete is finished, it's fine to spray a sealer on it to slow down the curing process. But remember, if the concrete is going to get coated or painted in the future, that "cure and seal" must be gone or removed.
  
  
• Wrong type of sealer used
  Certain types of sealers don't perform well in certain applications. For example, epoxy sealers shouldn't be applied to exterior surfaces because they don't allow the concrete to "breathe". Urethane sealers don't don't bond well with bare concrete and require a primer such as water based epoxy first. Always read labels before deciding which sealer to use.
  
  
• Surface not neutralized
  If you've done any acid etching or acid staining, you must neutralize the surface before sealing. Sealer will not bond well with an acidic surface. The easiest way to do this is with baking soda and water or diluted ammonia.
  
  
• Sealer applied too heavy
  This has happened to me before. I applied a heavy coat of sealer so I would only have to do it once. It took too long to dry and the hot sun blistered it. Remember that several thin coats is always better than one heavy coat. A 100% solids epoxy is the only exception to this.