Anode Placement in an E-coat Bath

Ask an Expert From: Products Finishing, from Finishing Help, LLC

Posted on: 9/1/2004

Question: Can you provide recommendations on proper anode placement in an electrocoat bath?

Question:

Can you provide recommendations on proper anode placement in an electrocoat bath? Specifically, how much distance should there be from the part entrance to the first anode as well as spacing of the anodes throughout the tank? M.R.

Answer:

Several factors are involved in answering your question. System and equipment designs are the first consideration. Is the system being run within the original design parameters? Design parameters involving the anode placement include: 1) throughput: square feet per minute, based on chain speed (feet/min) or carriers/hr depending on monorail or square transfer design; 2) “live” or “dead” entrance: whether the part is grounded as it enters the bath or is power only applied after the part is immersed; 3) total square feet of anode area vs. square feet of parts are often “stretched" when a system is run over design (and the addition of anodes to compensate).

Part quality requirements can also be a consideration since “hash marks” or film thickness variations (sometimes visible) can result if parts are subjected to coating voltage/power too soon upon entering the bath during a “live” entrance. Of course, line stoppages with parts in the bath are usually detrimental to the part's appearance (and also creates other quality issues) and should be eliminated or minimized in frequency and duration.

The actual placement of the anodes in the tank and its relationship to the parts being coated (distance and size) can also depend on the variety of parts being coated. If your system sees a fairly uniform quantity of parts (sq ft/min) and a uniform line speed, the anode placement is not as critical. If you have a lot of parts with deep recesses, tubular parts, or anything requiring maximum throwing power, the anode quantity and placement are much more critical.

The paint resin system and bath operating parameters (solids, temperature, anolyte concentration and control) must also be taken into consideration. While all operating parameters may not be able to be met at all times, some are more critical than others. As you can see, I did not give you a direct answer to your specific question. That is because there are so many operating parameters to be considered. While general “rules” are agreed upon between the equipment and paint suppliers during the design of a system, as the system changes things like anode placement need to be adjusted. I strongly recommend a group meeting of the equipment supplier (and their anode supplier), your paint supplier and your quality and management (since dollars may/will need be spent). Also be prepared to compromise between the parties, if the dollars are not available to satisfy everyone.

 


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