Polymer coatings containing cellulose nanofibers were applied to carbon steel for corrosion inhibition. The specimens were scratched with a knife-edge, and then polarization resistance was monitored in a sodium chloride solution. The polarization resistance of the scratched specimen containing nanofibers and corrosion inhibitor was higher than that of a polymer coating that contained only a corrosion inhibitor. The optimal mixing ratio of corrosion inhibitor for cellulose nanofibers was 4. Empty holes were confirmed on a cross-section of the polymer coating after the corrosion test, which showed that the nanofibers served as pathways for the release of the corrosion inhibitor.