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Climatic Conditions

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temperature, humidity & dewpoint

During the application of a coating, the presence of moisture in the environment or on the work surface, often results in a poor quality finish. Problems such as poor adhesion of the coating or premature corrosion of the substrate can occur.

To determine the likelihood of moisture affecting the quality of the finish, it is essential that the surface temperature, air temperature, relative humidity (RH) and dewpoint are all measured.

oven temperature data loggers - data recorders

Once a product has been powder coated to the required thickness, it must pass through an oven. During this baking (or stoving) process the powder melts, flows, gels and finally chemically reacts and cures. It is critical to the coating’s final performance and appearance that both the temperature and the time at temperature parameters are controlled.

It is imperative not only to ensure there are no hot or cold spots within the oven, but also that the temperature of the product being coated is sufficient to meet the technical specification of the powder coating. Failure to maintain the correct temperature profile can cause problems in the final performance and durability of the coating.

Variation of the oven temperature profile between production batches may lead to changes in the final coating’s gloss, adhesion and color. This can greatly affect the product’s quality and therefore could be the difference between success and failure.

moisture meters

One of the most regular causes of a coating’s failure is moisture. It is not sufficient to simply ensure that the surface is dry as often the surface of the substrate is the driest point – due to evaporation. Many substrates in industry today that are coated are porous and can absorb moisture. It is necessary to measure the moisture content within the substrate to reduce the possibility of subsequent coating failure.

When powder coating substrates which have a high moisture content – such as wood or MDF, steam will generate during the curing process damaging the new coating. Other substrates, which may have a high moisture content include concrete, fibreboard, plasterboard, gypsum and brick.

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