Retaining Pre-Construction Primers During Shipbuilding

Shipyards in the Far East and Europe often use weldable zinc silicate pre-construction primers (PCPs) in block construction. Although undamaged primers are not removed after block erection, the blocks are given a secondary surface preparation designed to permit good adhesion of the full protective system. Areas damaged through welding or erection are either blasted to Sa 2½ during block construction or power cleaned to St 3 after erection of the blocks. A full coating system follows this blasting or cleaning. This article describes some of the research that has been carried out to support this practice. This research conclusively demonstrates that certain PCPs can be retained without impacting coating performance. The author also argues for the necessity of a material standard for PCP. Since there are various PCP materials, their compatibility with the permanent system should be confirmed by testing. In order to effectively retain PCP for service, secondary surface preparation requirements and acceptance criteria must be developed and accepted.