2.7.1.1 Purpose of coating

The purpose is to protect the ductwork. This may be because aggressive substances are present in the air, for example in swimming pools. The air drawn in may also contain components that increase corrosion. Coating can also take place with the aim to make internal cleaning easier. Examples are mineral wool or hard foam ducts used in the food industry.

2.7.1.2 Coating types

There are several types of coating with various applications and usage requirements. Common types are:

• water repellent bituminous coating;
• polyester coating;
• polyurethane coating;
• anticorrosive primer.

In addition to the purpose of the coating, the application is also determined by the nature of the air duct and the area of application of the duct. The nature of the duct can be distinguished into:

• rectangular mineral wool;
• rectangular hard foam;
• rectangular galvanized steel sheet;
• circular galvanized steel sheet.

2.7.1.3 Instructions for use

Application of the coating should be in accordance with the supplier's instructions.