The Effectiveness of Power Tool Cleaning as an Alternative to Abrasive Blasting

Zone fabrication methods implemented by U.S. shipyards, incorporating block construction and zone outfitting and painting, have increased the need for more productive methods of secondary surface preparation. This "interim product" oriented ship construction process, as implemented by the Japanese, requires automatic centrifugal wheel blasting and shop priming of steel plate and structural. Surface preparation subsequent to fabrication, outfitting and erection is restricted to power tool cleaning. Abrasive discs, wire brushes (both radial and cup), and flap abrasive discs are the most frequent secondary surface preparation methods utilized. The effectiveness of this approach is enhanced by the selection and standardization of the coating systems specified. A National Shipbuilding Research Program study and inspection of the coating condition of Japanese ships with varying service lives verified that for many ship areas, this is a cost effective method of corrosion control. The implementation of Japanese technology by U.S. Shipbuilding has resulted in a retention of some historical U.S. practices. In the case of surface preparation and coating, it is often a requirement that shop primers be removed by abrasive blasting to a SSPC-SP-1 O Nearwhite cleanliness level prior to final painting, rather than over coated as is the Japanese painting plan. These new ship construction methods require that many areas of limited size be prepared and painted to repair damage from master butt welds and from the installation of outfitting materials by welding. Those areas requiring repainting are often in enclosed spaces near sensitive outfitting materials and equipment. The use of open abrasive blasting is not recommended due to the potential of damage to surrounding paint, outfitting items and equipment by abrasive ricochet and abrasive dust.