This project evaluated various cleaning processes and selected the most efficient process to implement. The project team also conducted a cost analysis to determine the most cost effective stage of construction to implement the selected process.
During new construction of Navy vessels, specifications require that steel surfaces meet certain requirements. The steel surfaces must be blasted to near-white conditions; have a certain surface profile; be free of contaminants, including conductive contaminants; and have the atmosphere meet certain requirements for blasting and application of ultra high solids paint system. The requirements ensure proper coating adhesion and minimize the possibility of defects such as blistering or peeling. Improper preparation can reduce the service life of a paint system. Currently, steel materials arrive at the shipyard from the mill and are grit blasted and applied with preconstruction primer. The primer provides protection against corrosion during the construction process. The steel is fabricated into various portions of a vessel and the primer is removed in areas that are welded. Since vessel construction can take several years, the fabricated or unfabricated steel can sit in the open environment for extended periods of time near salt water. Prior to final painting, the steel is grit blasted again, but the surface can have conductive contaminants on the surface, such as chlorides from salt water. Surface contaminants are potentially blasted into the surface during preparation, prior to either preconstruction primer or the final paint application. To remove these contaminants the surface must be cleaned again and can take up to three washes to remove the contaminants. The repeated washing and surface preparation, especially in tanks, can add significant costs to the painting operations as well as affect the schedule.
Implementation of improved preparation methods will provide a significant reduction in labor associated with preparing the surface and environment for blasting and painting operations. In addition, reduction in schedule delays will provide additional cost benefits.
The recommendations from this project will be implemented at NGSB-NN for construction of CVN 78.
StakeholderLCDR Brian A. Metcalf