Powder Coating Areas

Impact of Uncontrolled Humidity

In powder coating areas, high humidity causes various issues, including improper particle deposition, irregular film thickness, operational problems in spray guns, caking or agglomeration (clustering) of the powder particles, and a measurable negative effect on powder resistivity. In severe cases, powders exposed to high humidity cannot deposit at all.

Consequences of High Humidity

Additionally, humidity has a direct relationship with ion charge decay, particle deposition, and regularity of deposited thickness. It may cause the powder particles to stick to the corona electrode and thus quench the corona.

Additional Effects

Powder coating offers improvements in coating quality, efficiency, and economy by allowing the painting of objects through the spraying of a dry product without solvents, thereby avoiding pollution. Economically, overspray or excess powder can be reclaimed and reused through a recovery system. However, efficiency and reliability are affected by the interactions between the product’s chemical composition and the surrounding conditions, such as charge decay and relative humidity. Most powder coating spraying facilities do not control these conditions effectively.

Causes of Uncontrolled Humidity

The lack of controlled humidity and temperature in powder coating facilities leads to issues such as agglomeration of powder particles and inefficiency in the recovery system due to powder build-up in ducts, filters, and tubing.

Recommendation

Relative Humidity in Powder Coating Areas should be maintained at 40±5% RH at 24±5ºC.

Solution

Josem Solution

Josem Dehumidifiers and environmental systems provide complete control over both relative humidity and temperature within the powder spray booth area and often the entire coating room. This ensures an ideal environment for powder particles to sustain their charge prior to impact with the target.

Advantages

● Up to 15% less powder is required – due to uniform control of film thickness and reduced losses from powder coating build-up and agglomerates.

● Increased control over film thickness – by controlling the electrostatic field more precisely, achieving uniform coating of the target (particle deposition coupled with long-term ion decay).

● Increased system fluidising – the recovery system works nearer to its peak performance level due to reduced powder build-up in the duct, filter, and tubing.

● Reduced Agglomeration – dehumidified air reduces the powder’s ability to adhere to the inside surfaces.

● Reduced spray gun build-up – leading to a noticeable, marked improvement in quality.