The Coatings Surface Preparation and Degreasing Page

Member: NACE (National Assoc. of Corrosion Engineers), SSPC (Soc. of Protective Coatings)

Disclaimer: The comments below are offered only as suggestions and guidelines. All decisions regarding product selection, surface preparation, and coating application are the sole responsibility of the purchaser.

Surface preparation is, or should be, a significant portion of any epoxy coating project. Each surface and environment is different and unique. Some surfaces will accept coatings with minimal preparation, others will always exhibit problems. Experienced coating applicators will often refuse to accept these problem floors.

It is important to note that certain chemicals and materials added to the concrete before, during or after it is poured can cause a coating job to fail no matter what level of surface preparation is used. Suspects include special concrete curing compounds, chemical hardeners, bond/form release agents (bond breakers), and admixtures used to reduce/improve air entrainment, cement workability, gas forming, accelerated curing, etc.

It is nearly impossible to know ahead of time how much preparation is necessary. A minimalist will simply brush or sweep the surface (perhaps degrease a spot or two), apply the coating and hope for the best. Often this is all a homeowner can do (with perhaps a acid treatment to 'open up' the concrete). Fortunately, they often get away with this alone.

The problem with surface preparation is that it is often several months down the road before coating failures related to surface preparation may appear. By then it is too late to do much except laboriously remove all the recently applied coating and begin all over again. That said, for homeowners, the minimal approach can often be adequate.

If there is something new in 'surface preparation' it is an awareness of 'micro salt contamination' (semi-soluble salts) - on most surfaces (metals and concrete, fiberglass etc.) These 'salts' are not removed by sand blasting or grinding. High pressure water jetting (generally at 10,000 - 40,000 psi) will, if applied long enough, remove most of these salts. Flash rust, rust that forms on raw iron and steel minutes after it is wet blasted clean, shows the presence of these salts. On micro-salt free iron and steel (water wet or dry) rust forms very slowly.

These microsalts are a problem because they attract moisture, sometimes even pulling this moisture through the coating itself. The moisture and salts form blisters and tiny electrical cells that promote corrosion. The bottom line is that these invisible micro-salts can lead to premature coating failure.

We do not offer, but there are products called a micro salt remover wash product. You wet/wash brush the surface down with this wash and rinse off. It is an optional surface preparation step that could extend the life of your coating project be it on concrete, gunite, steel or metal, or even fiberglass.

IT IS GENERALLY MUCH MORE COMMONLY USED IN MARINE ENVIRONMENTS, USUALLY ON STEEL SURFACES (OR CONCRETE). I WOULD ONLY SUGGEST ITS USE IN GARAGES, BASEMENTS, ETC. IF THE FLOOR EXHIBITED CRYSTAL GROWTH (SPARKLES ON THE SURFACE) WHICH INDICATE MINERAL RICH WATER PERMEATING THROUGH THE CEMENT. THIS COMPOUND WILL HELP REMOVE THEM, BUT THEIR PRESENCE SUGGESTS A SITUATION WHERE GETTING ANY SORT OF SURFACE COATING TO STICK COULD BE A REAL PROBLEM. IN SUCH A SITUATION THE FIRST STEP WOULD BE APPLYING OUR BIO VEE SEAL PRODUCT.

The most common method of surface preparation is mechanical shot blasting which profiles the concrete by steel shot impacting the concrete at extremely high speed. This process is usually done by professional third-party contractors with minimum rates and prices. It is often not an affordable or practical option for the homeowner or ‘do it yourselfer'. The next best option is ACID ETCHING.

We now offer a much safer acid etch product (it is even considered NON-HAZMAT to ship). It even helps clean the floors. Nearly odorless and fumeless. Will not harm nearby metal surfaces. Called Prep N Etch™. CLICK HERE

Surface Problems Associated with Concrete - Comments

Grease and oils can create serious adhesion problems for coatings. Degreasing and washing may appear to remove the grease or oil, but in badly saturated situations residual oils/greases seem to remain and may cause a coating failure in the future. While not a definitive test, pouring a glass of water on the concrete and watching what happens can provide a valuable clue to coating adhesion. If the water quickly and evenly soaks into the concrete the surface preparation may be adequate at that point. More on degreasing concrete below (click here).

Moisture either in the concrete, and/or migrating through the concrete can cause coating failure as well. Taping a sheet of plastic to the floor and looking for moisture to form under the plastic is a crude but common test for migrating moisture. Some epoxies will handle a wet or damp surface better than others. Note that crystals forming on the surface due to water migrating through the mineral rich cement can create forces of up to 1,500 pounds of pressure as they grow in size. Few coatings can withstand such ‘anti-bond' forces.

Irregular surfaces on the floor will show through the epoxy and may be more noticeable after the epoxy is applied. Fill or patch any irregular surfaces on the floor before beginning.You can mix sand into a small amount of epoxy to form a slurry (the sand will decrease the amount of epoxy needed) to fill voids and cracks. Do not fill in or paint over expansion joints in the floor. The epoxy will crack, split and lift off when there is movement along the expansion seam.

If the floor is subject to heating and cooling cycles, air bubbles (that often form tiny craters in the epoxy) can sometimes be a problem. As the concrete heats up in the sunlight, the air in the void spaces of the concrete expands and forms a bubble that gets ‘stuck' in the thickening epoxy. If this is a potential scenario for you, apply the epoxy when the air/concrete is cooling off rather than heating up. When the temperature is falling the air contracts and will literally pull the epoxy into the concrete void spaces. After the epoxy has cured, the heating and cooling cycles are not a problem.

Surface Prep - company for those of you wanting professional surface prep...

Just wanted to follow up with you on our previous email. We work in MA, NY, NJ, PA, DE,
MD, VA, NC. Our minimum size job would be 200 Sq Ft. Happy Holidays to you and yours.

Regards,

Mike Hale
Director of Operations
Shot Blast Inc.
610-494-1330 Office
610-299-8088 Cell

Generally coating formulators like to see fresh (4 - 24 hours old) sand blasted surfaces prior to coating with the surfaces taken down to ‘white metal'. This often is not possible so lesser degrees of surface preparation are cautiously tolerated. How successful this lower stand is depends upon many factors including the coating itself, invisible contaminants on the surface, surface roughness (profile), humidity, etc. In some cases, wire brushing and/or high pressure water to remove weakly bonded rust, mill scale and dirt may be all that is possible. In such cases the rule is generally ‘coat at your own risk'.

Notes and Comments

Aluminum and Galvanized surfaces are generally considered to be the most difficult metals to coat. Aluminum flexes and forms a protective oxide surface to prevent corrosion.

Fresh galvanized surfaces are a soft surface that is meant to oxidize and wear away thus protecting the steel under it. Coating will lift off fresh galvanized surfaces within weeks if simply painted on. Fresh galvanized surfaces should be cleaned and acid etched prior to coating.

At this time I do not have the knowledge to make more specific comments about the priming or coating of Aluminum and galvanized surfaces.

Contact the American Galvanizers Association for additional help. Their number: 720-554-0900 marketing@galvanizeit.org

Rusted Surfaces

Rust converters (liquids that turn rust into a black inert product) are common and appear to work very well. I would personally use them on surfaces I could not remove all the rust from whether I was coating with epoxy or any other coating.

I would use our Aluthane primer on very rough surfaces as I have found that the only way to prevent rust from ‘bleeding through' even epoxy coatings, is to apply it very very thick (thick enough to bury all the metal's highs and lows to excess).

1) Initially clean the area with a detergent/degreaser (we offer one called 12000 Cleaner™).

2) An optional next step is the use of a propane torch to draw petroleum based oils and/or animal fats out of the concrete to the surface where they are carbonized.

3) Continue using a strong degreaser/cleaner. Repeat several times.

4) Top seal the cleaned concrete with our water-based concrete coating and sealer - Water Bond.

Finally, email us back with your questions or comments before you buy - EMAIL HERE

DISCLAIMER: Determining the suitability of coating the floor and the amount and nature of surface preparation required is the responsibility of the end user or customer and not the supplier of the coating product. The above information is not a recommendation by rather general information of a non-specific nature.

Progressive Epoxy Polymers, Inc.