There is provided the use of cellulose nanocrystals as a corrosion inhibitor for inhibiting corrosion of a metal object made of steel. The use includes using acid to impart ester groups onto the cellulose nanocrystals. The use includes dispersing an effective corrosion inhibiting amount of the cellulose nanocrystals having the ester groups within a composition comprising a carrier essentially consisting of water. The cellulose nanocrystals are provided in an amount equal to or greater than 0.1% by weight of the carrier and equal to or less than 3.0% by weight of the carrier. The use includes applying an effective corrosion inhibiting amount of the composition to the metal object such that the composition is adapted to inhibit corrosion of the metal object by 8% or more.