Silane and Siloxane sealers are two of the most reliable and widely used sealers within the concrete and masonry world.  Products such as Foundation Armor’s SX5000 combine both Silane and Siloxane to give contractors, business owners and homeowners a potent blend for maximum protection.

While Silane and Siloxane products are designed to be applied long term, there may be occasions when these sealers need to be removed.  This could be due to over application (concrete enhancement or darkening) or the desire to apply a decorative coating that would be compromised by a pre-existing silane or siloxane sealer. 

Planning ahead for your concrete sealing and coating projects is ideal but the world doesn’t function in a bubble.  For example, you may have purchased a property that was sealed by the previous owner.  When this happens, you need to assess the area to determine what material was applied (if possible), the current condition of the sealer or coating, if it needs to be removed and what means are necessary to remove the sealer/coating (mechanical vs chemical removal).

Silane and Siloxane products should be removed if you are planning to apply coating products such as Armor Epoxy or the Armor UTN60 (aliphatic urethane).  These products require an unsealed/prepped surface.  If the surface is not unsealed (bare) and diamond ground between 25 to 80 grit (CSP2- Concrete Surface Prep) or at least acid etched (CSP1) well, the new coating could fail.  Grinding or etching opens up the concrete pores to allow a coating to penetrate for better adhesion. An unsealed concrete surface will allow the coating to chemically bond on a molecular level.  If silane or siloxane are present on the surface, the epoxy or urethane bond will be compromised.

To prepare (prep) a concrete surface (already sealed with silane or siloxane) for a coating that is incompatible with silane and siloxane, you need to mechanically grind the surface (prep) and then chemically treat the surface with a concentrated sodium hydroxide cleaner (offered by local janitorial supply stores or homemade).  

Do not attempt to acid etch concrete treated with silane or siloxane, both are highly acid resistant (even when using muriatic acid).  By grinding the surface first, you will not only rough up (prep) the concrete surface but also remove superficial silane or siloxane.  Grinding before chemical treatment with a high ph cleaner reduces the amount of silane and siloxane and allows the chemical cleaner to penetrate and aggressively attack the remaining silane or siloxane.

A common question frequently brought up is “can acrylic bond to a surface treated with silane or siloxane?”  The answer is “yes” and “no.”  You should never apply water based acrylic over a surface treated with silane or siloxane (it will form a poor bond).  As for quality, solvent based acrylic lacquers (eg AR350, AR500, AX25), if the surface treated with silane or siloxane is porous or rough, the solvent/oil based acrylic should still bond.  If a small test is performed with solvent acrylic and it orange peels or separates into bubbles on the surface rather than laying down smoothly like a coat of paint, the silane or siloxane active ingredient concentration is too high.  This is more common on smooth, troweled concrete than on rougher, porous, broom finished concrete. 

Concrete surfaces that requiring removal of excessive silane or siloxane to allow for acrylic bonding or lightening of enhanced areas (darkened areas) do not necessarily require concrete grinding.  Using a high ph sodium hydroxide with a stiff bristle brush is often sufficient. If silane or siloxane has been over applied to a smooth troweled surface and a surface sheen is visible, a floor machine with an 80 grit screen or sand pad can also be utilized.  This will help remove superficial buildup of silane and siloxane prior to treating the concrete with a concentrated sodium hydroxide product.

Janitorial Sodium Hydroxide cleaners often recommend diluting with water but if the concentration of sodium hydroxide in the product is 5% or below(can check product safety data sheet), consider using it full strength.  This will keep the sodium hydroxide more concentrated to aggressively attack the silane and siloxane. Janitorial sodium hydroxide cleaners often contain solvents that may require proper collection and disposal (make sure to follow manufacturer’s disposal recommendations). 

 

 

Lye (sodium hydroxide) can also be mixed with water to make your own sodium hydroxide solution.  Concentrations of sodium hydroxide should not exceed 20% by weight which can cause moderate concrete deterioration. To put things in perspective, household drain cleaners usually have a sodium hydroxide concentration between 20 to 50%. 

 Keep the solution below 20% by weight (not by volume) and wear appropriate safety equipment (goggles, gloves, long sleeve shirts with pants etc).  To make a one gallon 5% sodium hydroxide solution (by weight), add 0.44 pounds of lye pellets or flake to one gallon of water (8.36 pounds is the weight of one gallon of water).  These pellets and flakes are typically close to 100% purity.  To make a one gallon 10% sodium hydroxide solution (by weight), add 0.93 pounds of lye pellets or flakes to one gallon of water).  If you don’t feel comfortable using pure lye pellets or flakes, sodium hydroxide is sold in 50% to 25% solutions at janitorial supply stores. These liquid concentrates can be diluted down more (follow manufacturer’s instructions).

Lye pellets or flakes should always be added to water and not the other way around. Mixing Lye with water generates heat so mixing in a little bit at a time is a good idea. Also consider keeping white vinegar (vinegar is acidic) nearby to neutralize the effects of sodium hydroxide if you do happen to get any on your skin. 

Larger volumes of a sodium hydroxide solution can be mixed in five gallon plastic PVC buckets.  It’s a good idea to mix no more than three to four gallons at a time to prevent the solution from spilling over the bucket edge.  A smaller container may be needed to scoop the solution from a bucket to a sprayer.  Some contractors will even pour a sodium hydroxide solution from a bucket directly onto concrete and push it around with a broom to evenly distribute the solution.

Once prepared, your sodium hydroxide solution can be applied to a surface with a plastic hand pump sprayer.  It’s best to use plastic sprayers and nozzles because sodium hydroxide will oxidize metal (corrosive). 

Prior to treating an entire surface with sodium hydroxide, run a small test area (a couple square feet) in an inconspicuous area.  Use a stiff bristle brush to work the sodium hydroxide solution into the surface treated with silane or siloxane. 

The trick is to keep the area wet with your solution and periodically scrub the surface with the bristle brush or broom.  It takes time for sodium hydroxide to degrade silane or siloxane.  The surface may need to stay wet with the solution for several hours to work effectively (apply more as needed).  After several hours, rinse off the area treated with sodium hydroxide solution and let it dry. 

After cleaning the surface and letting it dry, pour water on the treated area and verify that water penetrates and darkens the surface.  Water penetration and darkening confirms that the silane and siloxane have been removed to some extent.  If water is still puddling and the concrete continues to repel water, retreat with sodium hydroxide solution and continue scrubbing with brush as mentioned above. 

It’s not uncommon for concrete sealed with silane or siloxane to require several treatments with a sodium hydroxide solution in order to remove the sealer.  Silane/siloxane sealers such as Foundation Armor’s SX5000 or SX5000wb are high quality, commercial grade sealers designed for long term concrete and masonry protection (only requiring a light touch up about every 10 years on average).