High performance epoxy coatings are used to protect concrete and steel from chemical and mechanical attack in interior, exterior and marine environments. 2K epoxy coating systems consist of two or more components which, when blended and applied as a film, react chemically to form a protective film of high integrity, excellent adhesion, toughness and impact resistance without solvents or water added.
These coatings are applied in films ranging in thickness from several to over 150 mils. Coatings provide a protective impermeable barrier to elements which otherwise may attack the substrate. The chemical formulation and cross-link density of the coating material will determine its resistance to specific chemicals while resistance to mechanical loads, such as abrasion and impact, is a function of the physical properties and the thickness of the coating film.
Solvent-born coatings generally have a long pot life and are “thinner” and therefore, easier to apply. The “dry film” thickness or the film remaining after solvent evaporation is proportional to the solids content of the coating material and the applied or “wet film” thickness. ChemCo does not make solvent-born epoxies as we strive to make only 0 VOC coatings.
In order to avoid sag or runs and to allow proper solvent evaporation, solvent-borne coatings are applied as thin films. Application at low temperature or in thick films may cause solvent entrapment, giving rise to blisters or peeling.
Solvent-born coatings are particularly useful as primers, sealers, surface penetrants or where high film thickness is not required. In recent years, epoxy coatings have been developed which use water as the vehicle. Such products contain the coating materials as emulsions or dispersions, which upon application and evaporation of the water coalesce to form the protective film.
Solventless (“100% solids”) coatings contain no volatile ingredients, therefore, the final thickness of the cured coating is the same as the applied thickness. This category of epoxy coatings is manufactured by ChemCo Systems. Advantages of solventless over solvent-borne coating materials are:
When used on floors and decks, epoxy coatings can be skid-proofed by imbedding grit into the surface layer or reinforced by incorporating glass cloth. Trowelable coating materials of nonsag or mastic consistency are used for applications of thick layers on vertical and overhead surfaces.
Some high performance epoxy coatings for steel and concrete surfaces may chalk and discolor upon exposure to direct sunlight that causes their finish to turn dull. These features should be considered in exterior architectural coating applications.
Protecting Against Highly Aggressive Chemicals
Most applications requiring a high degree of chemical resistance are found in the manufacturing and chemical processing industries. Properly formulated and applied coating materials can stop the action of chemicals that rapidly deteriorate concrete and steel. Applications requiring high chemical resistance include:
Protecting Against Moderately Aggressive Chemicals
Epoxy coatings protect concrete and steel which are exposed to mild chemical attack from sources such as acid mist, organic acids and water containing corrosive chemicals. Concrete surfaces are often porous, subject to bacterial growth and difficult to clean. The glossy, tile-like, impervious natures of these coatings provide ideal protection in the following areas:
Providing Skid Resistance on Traffic Surfaces
The skid resistance of concrete, steel and asphalt surfaces can be improved by the application of a skid resistant coating. This consists of selected aggregate embedded into the coating. The aggregate dramatically increases the coefficient of friction of the otherwise smooth coating.
Areas that receive heavy wear due to high traffic speed and volume require a surface texture that will not be worn away or polished smooth. Skid resistant coatings are used to surface:
Coating Marine Structures
Epoxy coatings are used to protect concrete and steel marine structures as formulations are available to adhere to wet substrates. Marine coating use can be divided into two areas, splash zone application and underwater application. Both applications require the ability of the coating material to be workable, adhere and cure underwater; in the splash zone the material must resist wave action during application and after cure. Typical applications for the protection of marine structures include:
Effect of Temperature
Food and Potable Water
When the desired dry film thickness is known:
When using the manufacturer’s recommended spreading rate:
Skid Resistant Coatings
Two methods can be used to incorporate grit into a coating for service in areas which receive foot and light vehicular traffic. Where it is desired to build up thickness or develop a high degree of surface aggressiveness, grit is broadcast into the top coating layer to excess. After the coating has cured, the excess grit is removed. The resulting sandpaper-like texture can be moderated and rendered more easily cleanable by a final finish coat applied by roller. Naturally occurring, clean, kiln dried silica sands of 16 to 20 mesh are suitable for this application.
For light duty, where thinner layers or a less aggressive surface is desired in lieu of the broadcast system, a fine aggregate of 60 to 80 mesh can be mixed into the coating material and spread by squeegee as the final coat. Fine silica sands or emery grit may be utilized for this purpose.
|Standard Sieve No.||% Weight Passing|
Aggregate should be broadcast evenly over the surface and fall in a vertical direction to avoid displacing the uncured coating. Aggregate should be spread to an excess until the surface appears dry.
The quantity of the aggregate required depends on the thickness of the coating. Typical application rates of 28 to 30 square feet per gallon require 1.3 to 1.5 pounds per square foot of graded aggregate.
After the aggregate has been spread, all traffic should be prohibited until the surfacing material has cured sufficiently to bear traffic. Then, the excess aggregate can be swept up and reused if it is still clean and dry.
|Applied coating thickness (1000 mils=1")||Coverage per U.S. Gallon 100% Solids System|
|250 mils (1/4 in)||6.4 ft2|
|187.5 mils (3/16 in)||8.5 ft2|
|125 mils (1/8 in)||12.8 ft2|
|100 mils||16 ft2|
|62.5 mils (1/16 in)||25.5 ft2|
|50 mils||32 ft2|
|31.25 mils||51 ft2|
|20 mils||80 ft2|
|15.63 mils (1/64 in)||102 ft2|
|10 mils||160 ft2|
|5 mils||320 ft2|
|1 mil||1600 ft2|