Aluminium alloy (AA6082) substrate preparation for offshore repair coatings with a rotary impact tool

The contribution is concerned with the influence of bristle-blasting on texture, chemical status, and corrosion of aluminium (AA6082) substrates in synthetic and real seawater. The performance of an offshore epoxy coating, applied onto the substrates, is also investigated. Bristle-blasting generated substrates with a low level of contaminations and with a rather regular surface texture. It complied with requirements for offshore use in terms of substrate roughness and coating adhesion. The filiform corrosion tests delivered useful results. The cyclic corrosion test duration (3000 hours), however, was too short and the degradation was negligible. The coating performance was also evaluated during two years under real marine outdoor exposure in the splash zone and tidal zone in a North Sea location (Helgoland); the results were compared with the laboratory test results. For the first time, acceleration factors were calculated for the filiform laboratory test. The test generated very high acceleration factors, which depended on the location of the specimens during outdoor site testing.