Objective To study the protection property of the IMR21 nano composite coating on the airplane external structure in comparison with the polyurethane paint coating. Methods Corrosion failure behavior of the IMR21 nano composite coating and the polyurethane paint coating on simulated samples of the airplane external structure were investigated in typical accelerated corrosion environment. Results After accelerated corrosion for two stages of eight cycles in typical accelerated corrosion environment,bumps, cracks and exfoliation occurred on the coating surface. Compared with the polyurethane paint coating, there was less corrosion for the IMR21 nano composite coating. And the coating was corroded more seriously in the first stage than the second stage. Conclusion The results showed that the anti-corrosion property of the nano composite coating is excellent, and is hopefully to be used in the surface coating for anti-corrosion purpose in the processing and manufacturing, repairing and maintaining of the airplane external structure.