Studies on Corrosion of Metals in Surat Urban Environment

Corrosion rate of mild-steel, zinc and aluminium as well as the sulphation rate and atmospheric salinity rate have been determined in 1999-2000 under outdoor exposure at Surat representing urban atmosphere. Monthly corrosion rate of mild-steel, zinc and aluminium vary from 270 to 1050 (47 to 182 mu m/y), 17 to 59 (3 to 10 mu m/y) and 5 to 16 (2 to 7 mu m/y) mg/dm(2) respectively; whereas yearly corrosion rate being 1196 to 3205 (17 to 46 mu m/y), 41 to 115 (0.6 to 1.6 mu m/y) and 27 to 52 (I to 2 mu m/y) mg/dm(2) for mild-steel, zinc and aluminium, respectively. A sulphation rate was measured and was found in the range of 13 to 29 mg.SO(3)/mm(2)/month. Atmospheric corrosion rate of mild-steel indicates a close correlation with rainfall (r = 0.86) and number of rainy days (r 0.88).