Abstract
Water jetting is frequently used as a surface preparation method during maintenance of offshore assets. However, water jetted surfaces are exposed to formation of flash rust in the time interval between surface preparation and application of coating. The formation of flash rust increases with temperature, relative humidity and soluble salt contamination on the surface. In order to prevent flash rust to form and develop, corrosion preventing inhibitors have been utilized.
Three commercially available alkaline aqueous corrosion preventing inhibitors together with three different coating systems were selected for this study.
A wide range of standardized exposure tests were performed to investigate the performance of the different coating systems on various substrates under atmospheric and submerged conditions.
Based on the overall evaluation of the laboratory exposure test results it can be concluded that the corrosion preventing inhibitors tested has no significant effect on the performance of the coating systems during exposure testing when comparing to grit blasted substrates. However, samples with water jetted surfaces with light flash rust (WJ-2L) show in general an improved performance compared to grit blasted and substrates treated with inhibitors. This is likely due to a slight passivation of the steel surface by the formation of light flash rust. Subsequently, this study shows that use of inhibitors may be deemed un-necessary as long as the development of flash rust is limited. Moreover, if necessary to prevent the development of extensive flash rust, the use of corrosion preventing inhibitors is expected not to have any significant negative effect on the performance of corrosion protective coating systems.
