coating materials and application methods
INTRODUCTION TO
PAINT APPLICATION SYSTEMS
BY RON JOSEPH (1944-2011)
RON JOSEPH & ASSOCIATES INC., SAN JOSE, CALIF.
AND MICHAEL MURPHY
CONSULTANT, KILLIAN ENTERPRISES, VALLEY COTTAGE, N.Y.
A typical line for organic finishing of metals includes the following steps: precleaning,pretreatment, dry-off, primer application, flash-off and/or cure, andfinal cure. In some cases a primer or intermediate coating may not be used,and multiple applications of topcoat are not unusual. The combination of apigmented basecoat, often containing metallic flakes, and a final clear, lustroustopcoat is common today.
PRECLEANING
Procedures for preparation of metal parts for painting often include a precleaningstep. Removal of gross soils such as oil, grease, scale, weld spatter, lubricants,and other materials can be accomplished by mechanical means, with solvents,acids, or alkaline cleaning agents. Blasting, polishing, pickling, and solventdegreasing are described in the Metal Finishing Guidebook and Directory Issue. Whilethe purpose of precleaning is to remove the contaminants from the surface, thisprocess in and of itself does not provide any protection to the metals.
PRETREATMENT
The term pretreatment refers to a combination of chemical cleaning and conversioncoating. The purpose of a conversion coating is twofold. It improves corrosionresistance and provides a surface more accepting of the organic coating,subsequently enhancing adhesion…
