Green Epoxy Coatings

April 1, 2009

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One of the most environmentally-friendly methods of protective coating is epoxy coating, which is a product of natural and organic resin. Resin, which often comes from coniferous trees and plants, is valued for its ability to synthesize chemically and turn into useful products like varnish, adhesives, perfumes, and epoxy coating, among others. 

Epoxy resin is manufactured through a process of polymerization. The organic epoxy resin is combined with catalyzing agents, fillers, and pigments to turn into a dry powder which, when heated, melts and causes a reaction that allows the formation of complex cross-linked polymers. Once cured and dried, epoxy coating provides strong, UV-resistant, and permanent protection to steel materials. 

Fusion-Bonded Epoxy (FBE) Coating

Fusion-bonded epoxy coating is a method of applying corrosion-protective epoxy coating to steel pipes, rebars (reinforcement bars), pipes and valves. Epoxy powder is melted at temperature ranges of between 180 to 250°C (360 to 480 °F), and transforms into a liquid element that flows and adheres into the steel surface. Once the liquid powder dries, it cross-links or “fusion-bonds” to the surface of the steel material permanently, protecting the steel structure effectively and permanently. 

Fusion-bonded epoxy coatings are used extensively in industries requiring steel pipes and fittings that are corrosion-free. Because epoxy coating is made from environmentally-friendly materials, structures with epoxy coatings do not contain environmentally-hazardous solvents or substances that will come off and cause health and safety risks. 

The Epoxy Coating Process

Epoxy coating plants commonly coat bars that are pre-cut in straight lengths of around 40 to 60 feet. The bars are then cut and bent to meet project specifications. The bars are carried through a conveyor system and subjected to the epoxy coating process. 

To prepare steel surfaces for the epoxy coating process, blast cleaning is done to remove rust, scales and other contaminants from the steel surface. The end result of blast cleaning is a rough surface finish called a profile. The profile increases the effective surface area of the steel and provides better anchorage for epoxy coating when it is later applied to the steel bar. 

Blast cleaning involves the release of compressed air on to the steel surface, propelling abrasives like steel grit, garnet, or coal slag to hit the surface, resulting to pock marks that cleanses and roughens the surface. 

After the rebars have been blast-cleaned, they are heated and sprayed with dry epoxy powder. When dry epoxy powder is ejected from spray nozzles they are imparted with electrical charges that are automatically attracted to the already grounded heated bars. The dry powder melts and flows into the steel’s heated surface, anchoring to the ribs and deformations in the surface. The heat also induces a chemical reaction that transforms the epoxy powder molecules into complex cross-linked polymers, forever changing the material into its final state. 

A 30-second curing process solidifies the epoxy coating, with an air or water quench introduced to reduce the temperature quicker for easy handling. 

The process of manufacturing epoxy coating, and the coating process itself, are efficient and environment-safe, with little material lost to the atmosphere, even lesser waste, and zero contaminants. Because of the environmental consideration and to comply with environmental safety standards, epoxy coating remain a viable choice to protective coating. 

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