The inhibitive effect of cetyl trimethylammonium bromide (CTAB) on acid corrosion of mild steel in sulphuric acid at different temperatures has been investigated. Galvanostatic and potentiostatic studies were performed to determine the corrosion current, inhibition efficiency, passivation current and passivation potential range. The parameters so obtained were used to explain the effectiveness of inhibitor when present in different concentrations. Scanning Electron Microscopic (SEM) studies also help to understand the changes that take place on the surface layer with respect to change in CTAB concentration. The extent of corrosion inhibition has also been evaluated by comparing the micrographs obtained from SEM. The results obtained are in direct agreement with the electrochemical studies.