Browse Prior Art Database

Selective Electrostatic Coating of Nonconductive Substrates

IP.com Disclosure Number: IPCOM000078596D
Original Publication Date: 1973-Feb-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Ellis, TL: AUTHOR [+3]

Abstract

Presently, electrostatic powder coating processes are applicable only to metallic surfaces, because the part to be coated must be electrically conductive. However, by pretreating nonconductors with proper surfactants, as for example, a solution of about 10% TERGITOL* P-28 and 90% Isopropanol by volume, dielectric surfaces appear to attain sufficient electrical conduction to powder coat with an electrostatic process. Another unique feature of this process is the ability to selectively powder coat specific portions of the nonconductive substrate.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 52% of the total text.

Page 1 of 2

Selective Electrostatic Coating of Nonconductive Substrates

Presently, electrostatic powder coating processes are applicable only to metallic surfaces, because the part to be coated must be electrically conductive. However, by pretreating nonconductors with proper surfactants, as for example, a solution of about 10% TERGITOL* P-28 and 90% Isopropanol by volume, dielectric surfaces appear to attain sufficient electrical conduction to powder coat with an electrostatic process. Another unique feature of this process is the ability to selectively powder coat specific portions of the nonconductive substrate.

Powder coating can be applied by either a fluidized bed or electrostatic coating process. The fluidized bed process utilizes a tank in which powder is suspended by an upward stream of air passing through a diffuser plate in the bottom of the tank. The part to be coated is pre-heated in an oven to a temperature above the melting point of the coating powder. The heated part is then immersed in the fluidized powder and moved in a predetermined pattern, to insure particle penetration into all recesses and openings. As the particles contact the heated part they will melt, adhere, and flow out to form a smooth continuous film. Either thermoplastic or thermosetting powder may be used in this process, which permits the application of a coating in a single dip operation.

The electrostatic coating process is based on the principle that oppositely charged objects attract, and utilizes powder fed from a reservoir or fluidized bed to a source where a high-voltage, low-amperage electrostatic charge is applied to the particles. The powder receives the charge due to transfer of electrons from source to powder. The transfer takes place through contact with the highly charged source and through the surrounding ionized air. The part to be coated is electrically grounded. The charged powder is blown against the p...