Aesthetic Coatings for Steel Bridge Components.

摘要

The effectiveness of aesthetic coating systems for steel bridges was studied. Twelve 2-coat, 3-coat, and duplex coating systems were selected and subjected to a series of accelerated weathering and mechanical tests to determine their performance. The performance evaluation was made by considering gloss and color retention, coating discontinuities, rust creepage, and coating adhesion. Surface preparation and coating application procedures were given significant consideration. The best color and gloss retention was achieved by the 3-coat fluoropolymer systems, but they required higher materials cost. One of the two 2-coat systems performed nearly the same as the 3-coat polyurethane coating systems and the other showed a poor performance with significant color fading. Duplex polyurethane systems showed comparable performance to that of the 3-coat fluoropolymer systems but they performed better than the 3-coat polyurethane systems. This was primarily due to the added corrosion protection provided by the hot dip galvanization. It was found that proper adhesion in a duplex system can be achieved by following appropriate procedures for galvanization and surface preparation. Both duplex powder coated systems tested in this study experienced out-gassing problems during the initial application and did not show satisfactory performance.