Nanoparticle technology is a promising one for its unique properties, which can be utilised for different applications, for instance, as a corrosion inhibitor. This study investigates the corrosion-inhibition behaviour of Al₂O₃ nanoparticles synthesised by the Co-precipitation method. In this study, 800 ppm Al₂O₃ NPs are used as an inhibitor in a 1M H₂SO₄ solution for the Mild Steel (MS) sample at different times and temperatures. Experimental result shows that Corrosion inhibition efficiency is highest with 59.59% at 30℃ after 2 hours, and lowest with 8.22% at 60℃ after 12 hours. Corrosion efficiency decreases gradually with time and temperature. Characterisation of Al₂O₃ NP was done by SEM analysis, and the presence of Al₂O₃ NPs on the MS sheet surface was determined by FTIR analysis.