A Paint System for the Benjamin Harrison Bridge

About the report:

The paint system on a bridge, under normal conditions, should have a minimum life of ten years and it is desirable to have the paint last longer. The paint on the Benjamin Harrison Bridge is peeling, and numerous rust spots are showing through after four years of service, and upon inspection it became obvious that the life expectancy of the paint will not be met. The reasons for this seem to be twofold (1) the structure is exposed to rather severe corrosive fumes from the nearby chemical plants (no special paint system was designed for this type of environment), and (2) the 1958 specification that the bridge was painted under appears not to give sufficient protection over a long period of time. Mr. J. A. Tavenner, district bridge engineer in the Richmond District, stated that he has had 35 bridges repainted on 1-95 and 1-85, several whose ages were from 6 to 8 years, that had been painted under the 1958 specification. It is his opinion that the number 10 exterior white paint used did not bond well with the other coats.

It is the belief of the authors that for a corrosive environment such as the one that surrounds the Benjamin Harrison Bridge the following paint system give optimum protection: 1) Surface preparation near white blast clean surface in accordance with specification SSPC-SP10. 2) Primer at least 2.5 mils (or more, if recommended by the manufacturer) of approved zinc-rich paint (example: SSPC-PS 12.00) should be applied. 3. Finish coat(s) vinyl paints in accordance with specification SSPC-PS 4.00.

Authors