The inhibition characteristics of some thiazole derivatives against copper corrosion in acidic sulphate containing media have been investigated. The investigated thiazole derivatives were 5-benzylidene-2,4-dioxotetrahydro-1,3-thiazole (C10O2H7SN) and 5-(4 ' -isopropylbenzylidene)-2,4-dioxotetrahydro-1,3-thiazole (C13O2H13SN). In situ information on corrosion and inhibition processes at nanoscale range were obtained using scanning tunneling microscopy (STM) in combination with quartz crystal microbalance (QCM) measurements. XPS measurements were also performed to analyze the copper electrode surface. Based on these findings the role of molecular structure in corrosion inhibition has been discussed. The presence of the isopropyl group in the 5-IPBDT molecule produced far better protection against copper corrosion in acidic sulphate containing media than 5-BDT.