Evaluation of physico-chemical changes in sub-layers of multi-layer anticorrosive marine paint systems: Plasticizer and solvent release

Increased awareness of the environmental impact of solvent-based anticorrosive marine coatings has urged to predict long-term performance of a coating in order to make dry-docking less frequent. Each coating system was composed by three layers: topcoat, \ and primer. All samples were exposed to four different standard artificial weathering tests: a neutral salt spray test (NSS ISO 9227) and three cycles (QUV ASTM G53, ASTM D5894 and ISO 20340). Besides, the same samples were exposed to a natural weathering during 4 years in three different locations: Pipady (south of France), Kure Beach (North Caroline, USA) and Bandol (south of France). This research project focused exclusively on the degradation of the basecoat and primer by FTIR spectroscopy, PyGC/MS and dynamical mechanical analysis. Basecoat and primer binders formulated with dibutylphtalate as a plasticizer were found to strongly evolve during artificial cycle tests. An extensive diffusion of plasticizer was observed with a rise in Tg of the epoxy binder as high as 40 °C. The impact of these physico-chemical changes on the corrosion protection properties of the whole system were discussed based on electrochemical impedance spectroscopy (EIS) in 3 wt% NaCl solution, SEM observations, pull-off test and measurements of delaminated areas.