A Statistical Study Into the Performance of Organic Coatings Over Mechanically Prepared Welds in a Simulated Marine Environment

Effects of weld imperfection type, weld position, weld preparation grade, coating composition, stripe coating, inspection, and exposure duration on the corrosion protection performance of organic coatings on welds are systematically investigated by means of statistical methods. Three weld imperfections, namely weld porosity, undercut, and weld ripple, are considered. Two organic coating systems for marine applications are tested. Two weld preparation grades, namely P2 and P3, are included. Stripe coating (yes/no) and inspector level (three inspectors) are additional factors. The samples are exposed to a cyclic accelerated laboratory test according to ISO 12944-9 for varying exposure periods between 1 and 25 weeks. The target parameter is the number of damages in the coatings after exposure. The factor effects are evaluated with a full factorial experimental plan. Results of ANOVA analysis reveal that weld ripple and weld undercut require less thorough preparation (P2), when stripe coating is applied. Weld porosity, in contrast, requires a higher preparation grade (P3). Stripe coating can be omitted for the higher preparation grade. An empirical equation is derived to model the damage progress over exposure time.