Small-load rGO as partial replacement for the large amount of zinc dust in epoxy zinc-rich composites applied in heavy-duty anticorrosion coatings

A small load (e.g. , 0.5 wt%) of reduced graphene oxide (rGO) was used to replace a large amount (e.g. , 20-30 wt %) of zinc dust (ZD) in solvent-based zinc-rich epoxy composite coatings (ECCs) to maintain similar anticorro-sion, as well as to promote the adhesion/wear resistance of the corresponding coatings simultaneously.First, the corrosion protection of zinc-rich ECCs containing 20, 40, and 80 wt% of ZDs (denoted as DZ-20, DZ-40, and DZ-80, respectively) was investigated by performing a series of electrochemical measurements. The corrosion protection of ECCs was found to decrease in the order DZ-80 > DZ-40 > DZ-20. However, wear -resistance and adhesion tests of ECCs had the opposite trend of DZ-80 < DZ-40 < DZ-20 based on the method of ASTM 3359 and ASTM D4060, respectively.Subsequently, the small-load calcined GO at the operational temperatures of 300 degrees C and 1400 degrees C (denoted as rGO-300 and rGO-1400, respectively) was further incorporated into ECCs to partially replace large amounts of ZD and maintain similar anticorrosion performance and enhance the wear resistance and adhesion of the cor-responding ECCs. This finding indicated that incorporating a small load of 0.5 wt% of rGO-300 and rGO-1400 can partially replace 20 wt% and 30 wt% of ZD load, respectively, in ECCs. Accelerated salt-spray corrosion assays of scrapped test panels with and without coatings in an aggressive solution medium were used to evaluate corrosion resistance according to ASTM B-117. Results from the salt-spray assays of ECCs were consistent with those from the electrochemical measurements.