Abstract: A waterborne polyaniline microlatex is synthesized by a new modified microemulsion polymerization and the resulting microlatex could be applied as a coating for metal protection without further demulsification. A waterborne metal corrosion-resistant coating with good performance has been assembled using a mixture of the polyaniline microlatex with an epoxy emulsion as a prime coating, and a pure epoxy emulsion as a surface coating. The composite coating could enhance the open-circuit potential of a mild steel panel to circa 235mV comparing with that of the bare ones. They have not become blistered or rusted when they are exposed in tap-water for at least 3 months. It is indicated that the polyaniline microlatex is a sort of environmental friend coating.