Electrostatic painting of plastics using metal backing

The authors explain theoretically and experimentally the fundamental differences between spraying metal and plastic panels electrostatically. Mechanisms of charge dissipation from plastic surfaces are discussed, and a simple method is proposed for determining the electrostatic sprayability of plastic substrates. Using a one-dimensional analytical model, it is shown that the effect of charge accumulation can be minimized by appropriately placing a grounded metal backing behind the plastic substrate. Experiments were conducted in a spray booth environment, and the results showed good agreement with those predicted theoretically. Special metal backings with indentations and gaps were used to show that a mismatch between the plastic substrate and its metal backing can have a visually observable effect on the quality of the paint finish