Case 1

Cause of Defects

Degradation of the coating may have been caused by:

1. Poor UV resistance of the coating and imperfections in the coating may cause
2. Improper handling during which the coating may be scratched to expose the base metal to further attack by environmental agents. This may occur during scheduled maintenance works during which improper cleaning methods or equipment that causes excessive abrasive actions may be used.
3. Weathering and atmospheric pollution. Singapore’s aggressive environment of high rainfall and humidity and an excessive amount of salt laden air are main deteriorating agents. In urban and industrial areas, sulphur dioxide, unburnt hydrocarbons and particulate are also destructive. Fumes from the traffic contribute to harmful pollutants in the atmosphere and also cause stickiness on the panels.Rain water and moisture may contain harmful gases in weak solutions and these are absorbed by the dirt and grime on the roughened panels which promote further corrosion.

Even for high pollutants levels, corrosion was minimal at relative humidities below 60%. As the humidity was increased towards 80%, the protective oxygen film on the metal surface apparently broke down and corrosion began. Above 80% relative humidity, corrosion proceeded rapidly under the test conditions of 100ppm sulfur dioxide and various combinations of particulates.

For more details of different metals used on facade, see: Material Manual > Facade > Cladding > Infill Panels