Winning Coatings Combination Protects Bridge for Decades

In Pittsburgh, a visual inspection showed that the Homestead High-Level Bridge had only 1-2% surface corrosion after over 20 years in service.  

The long term durabilty is attributed to the winning combination of polyurethanes, U-104 and U-111.  Decades ago, U-104 was used to spot primer the worst areas followed by a prime coat of U-104 over the complete structure.  A finish coat of U-111 in light blue was then applied to provide an appealing gloss and color with grafitti resistant properties.

The secret to the longevity of U-104, even when applied over existing tightly adhered rust, is the ability of the small molecules to penetrate the rust and use the moisture that is fueling that rust as part of its curing mechanism.  During that process, the resin expands and locks tightly onto the existing rust. 

Over bare steel, laboratory testing has shown that 6 dry mils of U-104 will provide over 12,000 hours of protection in ASTM B-117 salt fog. U-104 is a single component product with considerable ease of application creating a robust primer.

U-111 was selected as the finish coat because of its ability to withstand decades exposed to the elements while still retaining the ability to be cleaned with harsh solvents to remove unsightly grafitti.  The extreme chemical reistance of the U-111 is a function of CFI's proprietary formula for this aliphatic polyester urethane, which yields a very dense protective coating.

 

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Homestead Bridge after 20 years in service Freshly painted Homestead Bridge
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