Addition of graphene oxide plates in cataphoretic deposited organic coatings

In the last few years more and more researches are focused on the deposition of paints containing graphene oxide (GO) to obtain a coating with a high corrosion protection performances [1-4]. Considering the good performance of cataphoretic coating deposition (uniform thickness, less substrate geometry sensitive) the idea, is to introduce GO in this kind of coatings. An epoxy-based cataphoretic bath was used. The graphene oxide plates, due to their affinity with epoxy resins, can improve the corrosion resistance properties of the coating obtainable by cataphoretic deposition, through a barrier effect. Different samples sets are considered to evaluate the more suitable supposition parameters to obtain a performance deposit. Starting from a simple single deposition step, which produced a little strange morphology deposit, other combinations made by 2 deposition steps were considered, in order to make the coating even more homogeneous protective layers. As comparison a GO free epoxy-based cataphoretic bath are carried out. Particular attention is therefore paid to the importance of the intermediate curing process, between the 2 deposition steps. First of all the GO flakes were characterized by observation at electron microscope. Then the morphology of the obtained coatings is observed both by optical and by scanning electron microscopy (SEM), to measure the thickness of the protective layers and their homogeneity and defective properties. Finally, corrosion resistance properties of the coatings are tested by salt spray chamber exposure and by electrochemical impedance spectroscopy (EIS). The use of a double deposition step, with 2 different baths, allows to obtain a more homogeneous, thicker coating, which therefore provides better guarantees in terms of corrosion protection. In a particular the most suitable system is made by a first deposition of a GO contained layer cured in a short time followed by a second GO free layer.