Organic rich coat ings generally require a higher

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for conductivity in inorganic zinc coatings since it is in a conductive, organic zinc-rich matrix. Organic rich coat- ings generally require a higher zinc loading to develop the zinc particle contact necessary for protection. Epoxy Epoxy binders are available in three types: epoxy ester; epoxy lacquer resin; and two-component epoxy. The two-component epoxies are most commonly used for painting structural steel. Epoxy resins of this type can cure by chemical reaction. The epoxy is generally combined with either of two types of hardeners (polyamine or polyamide) to form epoxy-polyamine and epoxy-polyamide. Epoxy-polyamine blends are more resistant to chemicals and solvents and are often used for lining tanks. Epoxy- polyamide paints are the most popular of all epoxy binders for use on structural steel. When exposed to weath- ering, they chalk quickly, but retain excellent chemical and abrasion resistant properties.
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SYSTEMS PAGE 30 Acrylics Acrylics can be supplied as solvent- or water- based coatings with varying performance characteristics. They exhibit good color and gloss retention, are single package, relatively low in cost and easy to apply. Solvent and chemical resistance, however, is lacking. They are best for interior, non-corrosive environments. Polyurethane Polyurethane binders are available in two types for painting structural steel: ! Moisture-cure polyurethane ! Two-component polyurethane Moisture-Cure Polyurethane Reacts with air moisture to cure. They produce the hardest, toughest coatings available in one package, and are increasingly popular due to the wide range of application and productivity advantages: ! Can be applied to cold damp surfaces ! Can be applied at temperatures below freezing ! No dew point restriction ! Year round application season ! Excellent recoatability ! Single component Two-Component Polyurethane Polyurethanes can also be reacted with products such as polyols, polyethers, polyesters or acrylics to produce extremely hard, resistant durable coatings. These are commonly used as topcoats. Alkyds Alkyds are available in both water dispersion and solvent-based formulations. Alkyd-oil vehicles can be formu- lated in flat and semi-gloss finishes over a wide compositional range. Generally, alkyds have poor color and retention properties and tend to chalk when exposed to sunlight. Their primary advantage is low cost. PAINTING GUIDES Sample painting guide specifications have been included at the end of the coatings technology section. Other coatings technologies can be considered. Consult your painting supplier for recommendations based on specif- ic project requirements.
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PAGE 31 SYSTEMS SPECIAL PURPOSE COATING SYSTEMS Intumescent Paint Intumescent paints are examples of special purpose coating systems. They can provide fire ratings for exposed steel for up to three hours. See the later section called "FIRE PROTECTION" for additional information on intu- mescent paints.
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