The climatic conditions in which a Belzona^® application is carried out are important, as they will affect: -

• The ultimate performance of the applied system
• The scheduling of the application

Temperature

Too high a temperature can lead to: -

• Increased coverage rate leading to thin areas
• Sagging
• Reduced working life
• Loss of wet-edge (solvent based coatings)
• Coating defects such as cissing

Too low a temperature can lead to: -

• Difficult to spread - material drags
• Reduced coverage rate – extra material required
• Poor wetting of the surface
• Extended cure times
• Incomplete cure

Changing temperatures can cause: -

• Condensation on the substrate
• Outgassing from porous substrates
• Irregular film thickness
• Product wastage

Humidity

Condensation or moisture on surface can lead to: -

• Flash rusting and premature corrosion on metallic substrates
• Poor adhesion
• Incomplete cure
• Bubbling/foaming (Belzona^® 2000 series)
• Loss of gloss
• Discolouration

Climate monitoring

Climate monitoring should take place prior to application and continue during application. Monitoring should include: -

• Substrate temperature
• Air temperature
• Relative humidity and Dew point
• Substrate moisture (prior to application on porous substrates i.e. concrete)

Substrate temperature

This should always be at or above the ambient air temperature to prevent condensation. On porous surfaces such as concrete, but including cast iron, application should be carried out with surface temperature falling. A rising surface temperature can lead to out-gassing with subsequent pinholes and defects in the coating.

Air temperature

This should be above the minimum specified for the product (18°C, 65°F, for Belzona^® 1391 & 1591) but not too high as to create application problems previously specified. Ambient temperatures above 40°C (104°F) should be avoided.

Humidity

The importance of Humidity becomes more critical at the high Relative Humidity levels (above 70%). This is because the dew point is more likely to be reached at these higher humidities.

The dew point is the temperature to which the air has to be cooled to cause condensation of water to occur. It is determined by measuring the air temperature with dry and wet bulb thermometers and referring to a Psychometric chart. This chart plots dry bulb temperature versus wet bulb temperature to show relative humidity and also to indicate the dew point for the specific ambient temperature and humidity conditions.

In practical terms the measurement of relative humidity allows the minimum allowable substrate temperature during the application to be predicted. This is important on applications that may take several hours or days to complete. For applications completed quickly it is sufficient to ensure the substrate temperature is 3-5°C above the air temperature. For larger applications the potential climatic changes, particularly falling temperatures, should be considered to ensure all the critical stages of the application are carried out correctly. This may involve ensuring the substrate temperature is maintained or, in the case of high humidity conditions, the provision of de-humidifiers.