Q. What should be the expected transfer efficiency of a square transfer system composed of one e-coat bath and two permeate immersion tanks? M.A.
A. The transfer efficiency is a calculation that determines the degree of utilization of the electrocoat material in the system. A transfer efficiency of 100 percent indicates that all electrocoat material has been transferred to the parts. Needless to say, achieving a transfer efficiency of 100 percent is impossible. So where does the e-coat material that is not transferred to the parts go?
The typical areas where electrocoat material is used up, besides on the parts, are in the racks, excessive film or film variation, excessive oven and cure conditions, and excessive permeate carryover and/or leaks. Other factors such as poor agitation also can contribute to poor transfer efficiencies. Low agitation or poor agitation patterns may lead to settling of paint solids.
Electrocoat industry studies and reports indicate that a transfer efficiency of 95 percent can be obtained with e-coat systems. This compares with transfer efficiencies of 45-60 percent for liquid systems and 60-80 percent for powder systems.
Maintaining high transfer efficiencies in electrocoat systems, especially in high-volume applications, can translate into significant annual savings on electrocoat resin and paste. Proper rack maintenance, good agitation, adequate cure and good ultrafiltration are typically the keys to good transfer efficiencies.
Characterizing the type of defect is essential in identifying the root cause and eliminating its source...
E-coat can produce uniform finishes with excellent coverage and outstanding corrosion resistance.
This paper is a peer-reviewed and edited version of a presentation delivered at NASF SUR/FIN 2012 in Las Vegas, Nev., on June 12, 2012.