Use of accelerated tests to estimate corrosion rates of roofing sheets

Roofing materials are important assets of our society however no material lasts forever. Atmospheric corrosion phenomenon leads to deterioration of materials. The objective of this study was to estimate the corrosion rate of metallic coated or pre-painted roofing sheets using accelerated testing method as compared to natural exposure. Accelerated tests were performed in ultraviolet light followed by salt spray at concentrations of 0.07% NaCl and 0.28% (NH 4 ) 2 SO 4 while in natural exposure the sheets were placed on racks under cyclic conditions of corrosive environment. The gloss and fade variations of pre-painted sheets were determined using spectroguide. Variations occurred within 10.5 days for accelerated tests and 90 days for natural conditions. Correlation analysis on gloss and fade variations under accelerated and natural conditions showed that for gloss R 2 = 0.994 while fade R 2 =0.831. Mass loss for galvanized and galvaluminized materials was determined using Shimadzu XRD-7000. Mass loss occurred within 10.5 days for the accelerated tests and 90 days under the natural conditions. High correlation indicates that accelerated tests can be used to estimate corrosion rates of roofing sheets under different corrosive environments.