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Misc. problems in CED (cathodic electrodeposition) coating

This thread covers many CED problems, but Pinhole problems have been moved to Thread 57561


Q. Hi, lately I am assigned to do research and development on CED. And lately my result is something like this picture.

32574-10

There are many dots in the surface of the working object. Maybe anyone here can help me what might be the cause of the dots?

Thank you

Josafat Malau
Employee - Indonesia, Jawa Timur
January 12, 2024







⇩ Closely related postings, oldest first ⇩



Q. I am getting the problem of half-coating and half no-coating in CED. Defect rate is low. I have checked the contact points and there seems no problem with that. Defect rate might be around 1 in 100.

Madhukesh Jamadagni
painting shop - Mysore, Karnataka, India
2004


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

Manish Dhyani
- New Delhi




SUGGESTED ELECTROCOATING, CED, ELECTROPAINTING BOOKS
for Shops, Specifiers, & Engineers   (affil links)


"Electrocoats: Formulation and Technology" by Bruggemann & Rach (2020)
avail from eBay, AbeBooks, or Amazon

"Electrophoretic Deposition (EPD)" by Nathan Bass (2017)
avail from eBay, AbeBooks, or Amazon

"Electrocoating: a Guidebook for Finishers" by Electrocoat Association (2010)
avail from Amazon

"Electrodeposition" by Rodger Talbert (1996)
avail from Amazon

"Electropainting: A survey of principles and practice" by Reginald Leslie Yeates (1980)
avail from AbeBooks, or Amazon

"Handbook of Electropainting Technology" by W. Machu (1978)
avail from AbeBooks, or Amazon

Q. Please send me the information of the defects of CED COATING, and provide the answers for the questions relating to the topic. I will be grateful to you.
THANKS,

MANMOHAN Singh
- Faridabad, Haryana, India
2006


A. Hi cousin Manmohan. If you are having a problem, please try to detail your situation; and feel free to send pictures to mooney@finishing.com for posting here. We have many Q&A's about CED Coating in this forum and I am confident that someone here can help you with it!

Regarding the general issue of possible defects & solutions, we have listed six books on the subject along the right side of this page ⇨
and suggest that you try to get access to one or more of them.

Luck and Regards,

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




Dirt in Coating

Q. We are facing dirt/impurities problem on parts after CED coating.

Kalidas Suryawanshi
- Pune, India
2007


? Hello, cousin Kalidas. if you can give us some info, I think our readers can help! Send some pictures, and tell us what you can.

If you lack sufficient data, the paint vendor, system vendor, or an e-coating consultant may be able to help. Good luck!

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



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.

Gurvin Singh
Mohali, Punjab, India


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

baljeet_babli_singh
Baljeet Singh
- Ludhiana, Punjab, India


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..

Shivam Pandey
Process incharge - Fharidabad Haryana
August 31, 2021


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.

Dhirender Pratap Singh
Senior Executive - Looking Paint Process - Haryana, India
September 21, 2021


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

Amit sharma
- jamshedpur, India
July 11, 2022




Ra value of CED coating

Q. PLEASE TELL ME HOW TO CHECK THE Ra VALUE OF CED COATING.
WHAT IS THE RANGE FOR OEM VEHICLES?
WHAT ARE/IS THE INSTRUMENT USED FOR CHECKING RA VALUE?

KAPIL VASHIST
ENGINEER - INDIA
May 20, 2009


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

Thanks
SURYA

SURYAPAL _
- DELHI, INDIA


A. Hi,

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

Anand.

V. Anandaraj
- Chennai, India




Dissolution of CED Coating

Q. Hello, could anybody help me understanding the reason for dissolution after CED coating on wheels? It mainly happens with small wheels.
Regards,

Ale luso
wheels - Bologna, italy
April 11, 2014


A. Hi Ale. Sorry, but I don't understand what you mean by dissolution after CED coating. Where, when, and under what conditions is this happening? Can you offer a synonym or expand upon your situation, please. Thanks.

Regards,

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


Q. Hello, I'm sorry, pictures were missing. We produce steel rims and it happens that a few rims (1 to 10% depending on the reference) leave the CED coating bath only half coated; more precisely only the first half on the rim is coated.

32574-1 32574-2 32574-3

I've attached an explicative picture. Which parameters could cause it in your opinion?
Kind regards,

Ale luso [returning]
- Bologna, italy
April 15, 2014


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

Thanks
Surya

Sp singh
- Faridabad, India




Not getting e-coating despite proper voltage

Q. WE ARE GETTING NO COATING ON THE COMPONENT (LOAD BAR). WE GETTING THE PROPER VOLTAGE BETWEEN BOTH POLES AS PER SETTING BUT THE CURRENT IS GOING ONLY 15-20 A DC. OTHER HAND IF WE WILL PROCESS ONLY 2 OR 3 PARTS, WE ARE GETTING COATING AT THE COMPONENT. LET ME KNOW THE ACTUAL PROBLEM AND ALSO IF IT CAN BE THE PROBLEM OF RECTIFIER.

OMPRAKASH YADAV
- NOIDA,UTTER PRADESH, INDIA
September 25, 2014
September 25, 2014


A. Hi,

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

Your problem maybe 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.

harry_parkes
Harry Parkes
- Birmingham, UK


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

Dr. Halim Polat
- istanbul Turkey


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.

Selvakumar.S, Chennai
- Chennai, Tamilnadu, India




Finish coat cracked due to inferior E-coat under it?

Q. Working with a shop on a repair that used an aftermarket bumper cover (non steel) and when the finish coat was applied it cracked all over as it started to cure.

32574-4 32574-4t

Shop says it's inferior E-coat used by the aftermarket supplier. Your thoughts?

Phil W [last name deleted for privacy by Editor]
insurance claims - Houston, Texas, USA
January 21, 2015


A. Hi Phil. I wouldn't expect a body shop to be a fully instrumented coatings science laboratory able to analyze precisely why an aftermarket bumper cover was unpaintable.

... but I would trust people who paint cars day in & day out to be able to reliably paint proper substrates; it will surprise me if anyone can look at the photo and contradict the body shop's assertion.

opinion!   But how did it become your problem unless you told them to use aftermarket parts? If you did, it's on you to prove that the parts are okay. Don't expect the finishing industry, whose reputation gets tarnished when consumers end up with inferior parts when the insurance industry decides that replacement components don't need to be equivalent to OEM parts. All costs associated with inferior aftermarket parts are the fault of the insurance company.

No one should be allowed to substitute inferior parts, and problems like this are only the tip of the iceberg of long-term problems the consumer gets stuck with. Consumer Reports has written repeatedly about this problem of manifestly inferior replacement parts being specified by insurance companies. Good luck.

Regards,

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




Q. We are getting water spots and water or paint flow marks on the components after curing. We could identify the marks if we blow air after UF and before curing. How to eliminate these marks?

RAJAGOPALAN SESHADRI
CED COATING UNIT - Hosur, Tamilnadu, India
February 17, 2015


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.

SANJEE KUMAR
- ALLAHABAD, India
July 16, 2022




CED Painting Defect: 'Partial Coagulation'

Q. Please tell me about the CED painting defect of "partial coagulation" on child bicycle parts like swing arm, center stand and prop stand.

Prince Kumar
- gurgaon, haryana, India
August 1, 2015




Anodic to cathodic cell ratio in CED electrocoating

Q. Hi sir I want to know how much ratio in anodic and cathodic cell in CED bath

Sandeep kalidas raut
CED coating - Mumbai, Maharashtra, India
December 16, 2015


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

Thanks

Shivam Pandey
Process incharge - Faridabad [India]




Q. How to calculate the anode cell ratio in CED? Please, I am preparing for an interview and I need a clear answer.

BALA mani
private automobile company - Chennai, tamil nadu, India
March 16, 2016




CED Bath: Why/How has Sodium Increased with no other changes?

Q. Hello sir,
There is increase in the sodium content in the CED bath while all parameters of the bath are as per specification. Please suggest.

kalyani Argade
- Pune, Maharashtra India
March 31, 2016



simultaneous replies

A. Na content increases due to carryover of alkaline cleaners from P.T. line. Rinse parts thoroughly.
Have you added any tubular part recently in your production?
If so, check the carry over.

Avinash Vidhate
- Nasik, Maharashtra, India


A. An increase in the sodium level can be due to drag out from your alkaline cleaner. Are you using a sodium hydroxide based cleaner?

Dan Mack
- Horicon, Wisconsin USA




Q. Hi
What is maximum oven temperature for CED jobs?
Can we put CED & Power Coated jobs into one batch for Curing the coatings?

Please give details.
Thanks & Regards

Vivek Nirgudkar
powder coating & CED coatings - Pune, Maharastra, India
June 27, 2016


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.

Saravanan P.M
- Chennai, Tamilnadu, India


thumbs up signHi. That sounded like "expert comment" to me. Thanks!

Regards,

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




Q. How can we control roughness after CED coating? It is varying a lot. I want to maintain it to its standard.

monu mittal
- gurgaon, haryana, India
March 24, 2017


A. CHECK EARTHING.

PRASHANT KUMAR
CEPL - PUNE, Maharashtra, India




Anode Cell Area Calculation

Q. Can anyone please help me how to calculate the Anode cell area/ no. of Anode cells required in ED Coating process according to Area of Component or Tank size?

Also how to select the range of Rectifier?

Arunprabhu A R
Designer - India
October 7, 2017


Q. Can anyone please help me how to calculate the Anode cell area/ no. of Anode cells required in ED Coating process according to Area of Component or Tank size? How do we know what is the capacity of anode in relation to surface area? How much surface area is covered by one anode?

We manufacture wheel rims; when we hang these on a basket after CED coating some area is unpainted where they are touching each other. What is the real cause of this

Rohit Kumar
- Faridabad haryana , India
November 27, 2017




Masking for CED Coating

Q. Hi
We'd like to mask the wheel rim knurling during CED process.
Please suggest any masking.

Felix prasad
- Chennai, India
January 22, 2018



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