Improvement of the edge protection of an automotive electrocoating in presence of a prepared epoxy-amine microgel

The present study developed a method for modification of the cathodic electrocoatings formulation in order to improve their edge protection and anti-corrosion properties using epoxy-amine based microgels. An epoxy-amine microgel was prepared by reacting an epoxy resin, with methyl ethanolamine and diketimine. The prepared microgel had a mean particle size of 120 nm. Various contents of the microgel (2-8 wt%) were incorporated into an automotive electrocoatinging bath. The pigment to binder ratio was kept constant (1:6) for all samples except for the HPBR (high pigment to binder ratio sample, 1:4). The effect of the microgel on the rheology of the coatings was investigated by rheometric mechanical spectrometer (RMS). Minimum melt viscosity has increased significantly in presence of 4 wt% of microgel particles. The micrograph images obtained from field emission scanning electron microscopy (FE-SEM) indicated that the prepared epoxy-amine microgel, had a microsphere shape. Dynamic mechanical thermal analysis (DMTA) was used to study the effect of microgel particles on the curing behavior and the cross-linking density of the coatings. Pull-off test was used to investigate the microgel effect on adhesion strengths of the electrocoating. Glossmeter and profilometer were used to analyze surface morphology. Microgel particles did not significantly change gloss and roughness of the electrocoatings. Electrochemical impedance spectroscopy (EIS) and salt spray testing confirmed that in presence of 4 wt% of microgel, the anti-corrosion properties and edge protection were improved significantly.