What Went Wrong?
The Nuts and Bolts of Corrosion

In this situation, corrosion has appeared shortly after construction of this building on the angle bracket supports holding an exterior awning. Upon inspection, two factors become visible. First, the coating has been damaged by the re-torquing of the bolts after painting. Apparently, no following touch-up work was performed or requested in these areas.

The second problem is that there was no primer applied to the bolts before top coating. In other areas that had not been re-tightened or had the paint damaged, there was some evidence of corrosion forming under the film and leaving oxide streaks on the lower painted surface. These areas would be expected to fail within one year and require grinding, priming and re-finishing -- or replacement if the damage was too extensive.