| Abstract: | Corrosion resistance of unpainted and coil-coated sheets under atmospheric exposure An extensive study was carried out to compare the corrosion behaviour of unpainted and coil-coated hot dip galvanised and Galfan-coated sheets under atmospheric exposure. FIat and roll-formed test pieces with various metallic and organic coatings were exposed to atmospheric weathering at five different locations for 9 years. The corrosion behaviour of unpainted specimens was determined quantitatively by measuring the loss of metallic coating thickness and by visual assessment of red rust on surfaces and bends. In the case of organically coated specimens formation of red rust and blistering on surfaces and bends was assessed visually and creepage at scores and cut edges was measured. The results show that Galfan coatings are subject to much slower weathering than hot dip galvanised coatings. It is concluded that in most applications users could select the next lower coating thickness group when using Galfan instead of hot dip galvanised sheet. Visual assessment of corrosion damage (red rust, blisters, creepage) also leads to the overall conclusion that both unpainted and coil coated Galfan perform much better than hot dip galvanised sheet in natural weathering. The advantages of using Galfan especially for building applications are thus being established. |
