Misc. problems in CED (cathodic electrodeposition) coating

Please share photos of these problems.

A. Check CED bath parameters. Check for bath and anolyte conductivity.

A. Hi cousin Manmohan. Others, perhaps suppliers, might have free booklets available of the sort you seem to be seeking, but we don't. However, we've listed six books on the subject if you want to you want to try to get access to one or more of them.

This public forum is more suited to helping people work their way through a specific problem they are encountering; to take best advantage of what we're able to do, please try to detail your situation; feel free to send pictures to mooney@finishing.com for posting here. Thanks.

Luck and Regards,

A. Dirt can come due to improper cleaning in the pre treatment line. It can be due to dirt in the E-coat tank. It could be due to dirt in the rinse tanks after E-coat. It could be due to dirt being blown around in the oven with the forced circulation. It could be because of one or more than one of the reasons above. And the reasons above could also be due to improper housekeeping or ingress of dirt & dust in your E-coat shop.

Test each and eliminate. I assure you this does not require NASA technology.

A. Check for sludge material in phosphate bath ... if it is high, then desludge it immediately. This will solve your problem.

A. Dear kalidas
Reason of dust ...
1- not proper manual cleaning
2- kod/degreasing FAL pointage down
3- contaminated rinse
4- sludge increase in phosphate tank
5- contaminated DI water..

A. 1. Kindly install filter housing just before CED tank.
2. Use 10 micron filter in CED bath for 10 days and plan to use 10 micron bag filter once in three month.

3. Check CED bath circulation :- it should be properly work, causes of poor circulation paint settling started in bath then generate dust when settling burst.
4. Check incoming material quality first :- it should be dirt free , need & clean material required for ced.
5. Add Solvent as per spec. Less solvent also create dirt or improper finish.

A. Otherwise you can check oven and chamber filter cleaning and air quality.

A. Ra is checked by roughness gauge.
Better you ask your paint supplier for Ra Parameters.

Thanks
SURYA

A. Hi,

Normally Ra value can be checked with use of Perthometer. try it.

Anand.

A. Hi Jayesh.

Presumably you phosphatize the components after machining and before CED coating? Phosphatizing significantly increases the Ra. So a question might be what is the Ra after phosphatizing? Armed with that information you would be better equipped to figure out where the bulk of the roughness is coming from and whether to focus on the phosphatizing or the CED step itself.
Luck & Regards,


Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

! Dear Sir,
For CED coating of aluminium, phosphating is not done; instead chromatising is the process.
Please let us know the process what exactly he is doing.

Good catch Avinash :-) I guess I wasn't thinking; you are right of course that for pretreatment of aluminum, chromating is much preferred over phosphating! Regards, Ted Mooney, P.E. RET Striving to live Aloha finishing.com - Pine Beach, New Jersey 🙏 It's your humbleness 🙏 Avinash Vidhate [returning] - Nashik, Maharashtra, India April 6, 2024 Thanks so much for your kind words. Although I've been in the industry a long time, I never actually ran a metal finishing line of any sort -- so there is a gaping hole in my knowledge which I constantly have to rely on others to fill :-) Regards, Ted Mooney, P.E. RET Striving to live Aloha finishing.com - Pine Beach, New Jersey

A. Hi Ale. Sorry, but I don't quite understand what you mean by dissolution after CED coating. Can you offer a synonym or expand upon your situation, please. Thanks.

Regards,

A. Sir,
It might be helpful to
- increase bath & anolyte conductivity,
- change the loading position.

Thanks
Surya

A. Hi,

I'm assuming that that you are using a cataphoretic resin. If it is anophoretic then the advice still stands but swap the words "anode" and "cathode",

Your problem may be caused by the anodes restricting the current flow. So, when you put large areas of work in the bath the cathode current density is too low to initiate deposition of resin. Suggest:

1) Increase the number of anodes
2) If you are using anode boxes make sure that that they are filled with electrolyte of the recommended conductivity.

A. Increase anode area
Increase voltage
Increase solid in bath
Increase bath temperature
That is it.
Regards,

A. Reasons for poor CED coating:

1. Poor electrical contact to the job to be coated.
2. Low cathode-anode ratio. This will be considered in plant design itself. But this may vary if the anode gets corroded; in case of CED, check the anode condition.
3. If ramp up voltage is too high, some parts may get poor coating.

Since amps is showing very low, it means the rectifier to be checked.

A. Hi Phil. Body shops aren't coatings science laboratories, able to analyze why an aftermarket bumper cover was unpaintable -- but I do trust them to be able to reliably paint proper substrates.

opinion!   If these are aftermarket parts specified by an insurance company, someone failed their job of sending the parts to a coatings science laboratory to prove they're okay.

But this problem is the tip of the iceberg; the consumer gets stuck with the long term problems that don't immediately manifest like this one did. Consumer Reports has written about the problem of insurance companies and body shops using inferior replacement parts, such as non galvannealed panels, and the problems which only surface after time has passed. We offer Aloha here, but can't side with offering less than what is required. Low quality sucks. Good luck.

Regards,

A. Extend your bus bar to achieve live entry in place of dead entry in CED bath. Or You have to keep it completely wet or completely dry before entering CED bath at water rinse stage before entering into CED tank: Because partially wet or partially dry body can cause such kind of problems.

A. Dear sir
Greetings
Anode and cathode ratio-1:14

Thanks

A. Generally CED Paint cures at 150 °C / 20 minutes or 160 °C / 10 minutes Effective Metal Temperature. Oven Air temperature can be set depending on the Material thickness (Component) and time available for Oven curing.

If it is thin material may be 170 °C, 30-40 minutes more than sufficient to cure. In case of thick material like Forging or Casting we may go ahead up to 200 - 220 °C.

Logically we can bake both Powder and E.Coat in the same oven and there will be not any issue in the baking as long as if we meet the baking window criteria.

However E.Coating is a 'wet' process and it is cured in an oven to promote cross-linking. Solvent and Moisture evaporation takes place. Whereas in Powder, Curing causes the particles to melt and also serves as the catalyst for a chemical reaction that produces the desired finish. Both are different process.

During the Hot air circulation sometime loose powder particles deposits on the E.Coat surface before curing causes finish problem. Hence I would not advise Technically. Let us wait for some expert comment please.

Hi. That sounded like "expert comment" to me. Thanks!

Regards,

A. CHECK EARTHING.