Corrosion rate of mild-steel (MS), zinc and aluminum as well as the sulphonation rate was determined during 2005-2007 under outdoor exposure in an Urban atmosphere at Valsad (Dist. Valsad) situated in South Gujarat, India. Monthly corrosion rate vary from 77 to 824, 19 to 109 and 1.5 to 17.8 mg/sq.dm correspond to MS, zinc and aluminium respectively, whereas the yearly corrosion rate vary from 2575 to 3667, 181 to 459 and 8.3 to 37.2 mg/sq.dm for mild-steel, zinc and aluminium respectively. Monthly corrosion rate was found in the decreasing order : mild steel < zinc < aluminium. Corrosion rate of these three metals was found more in rainy seasons than the rate of winter and summer season. There is a considerable loss of corrosion rate during exposure for one year of mild steel. Monthly corrosion rate of mild steel indicate a close correlationship with rainfall (r = 0.65) and positive correlation with sulphation rate (r = 0.54). No correlation appeared to exist between temperature and corrosion rate of mild steel, zinc and aluminium.