Misc. problems in CED (cathodic electrodeposition) coating
A discussion started in 2004 but continuing through 2018(2004)
This thread covers many general CED problems, but
PINHOLES have been moved to Letter 57561, "Pin holes in CED e-coating"
Q. I am getting the problem of half-coating and 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
A. Check CED bath parameters. Check for bath and anolyte conductivity.Manish Dhyani
- New Delhi
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.
- Faridabad, Haryana, India
A. Hi cousin Manmohan. If you are having a specific problem or problems, please try to detail your situation. We have numerous Q&A's about CED in this forum and I am confident that someone here can help you. Regarding the general issue of possible defects and solutions, at least two full books have been written on electrocoating, and we can suggest that you try to get access to one or both of these =>
Luck and Regards,
Ted Mooney, P.E.
Pine Beach, New Jersey
Dissolution of CED CoatingApril 11, 2014
Q. Hello, could anybody help me understanding the reason for dissolution after CED coating on wheels? It mainly happens with small wheels.
wheels - Bologna, italy
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.
Ted Mooney, P.E.
Pine Beach, New Jersey
April 15, 2014
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.
I've attached an explicative picture. Which parameters could cause it in your opinion?
- Bologna, italy
May 12, 2014
It might be helpful to
- increase bath & anolyte conductivity,
- change the loading position.
Not getting e-coating despite proper voltageSeptember 25, 2014
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 30, 2014
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.
- Birmingham, UK
October 26, 2014
A. Increase anode area
Increase solid in bath
Increase bath temperature
That is it.
- istanbul Turkey
November 17, 2014
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.
- chennai, Tamilnadu, India
Finish coat cracked due to inferior E-coat under it?January 21, 2015
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.
Shop says its inferior E-coat used by the aftermarket supplier. Your thoughts?Phil Wells
insurance claims - Houston, Texas, USA
A. Hi Phil. I would not 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 certainly trust a body shop -- people who paint cars day in & day out -- to be able to reliably paint proper substrates, and to 'fess up if they made a mistake. Thanks for the photo, but it will surprise me if anyone is able to look at it and contradict the body shop's assertion that the bumper guard is defective (although yes, after significant testing, a coatings science laboratory might be able to).
opinion!Why does the body shop feel it's your problem unless you told them what parts to use? If you did tell them to use aftermarket parts, it's on you to prove that the parts were paintable and the shop screwed it up.
All costs associated with the quality issues of inferior aftermarket parts should be 110% the responsibility of the insurance company if they specified them. Neither body shops nor insurance companies should be allowed to substitute parts which are inferior to OEM parts, and initial problems like this are only the tip of the iceberg of long-term problems the insured consumer is left with. Consumer Reports has written repeatedly about this problem of manifestly inferior replacement parts being specified by insurance companies, but apparently if the government isn't watching them, that's exactly what they do. Good luck.
Ted Mooney, P.E.
Pine Beach, New Jersey
Water and paint flow marksFebruary 17, 2015
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
CED Painting Defect: 'Partial Coagulation'August 1, 2015
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
Anodic to cathodic cell ratio in CED electrocoatingDecember 16, 2015
Q. Hi sir I want to know how much ratio in anodic and cathodic cell in CED bath
CED coating - Mumbai,Maharashtra, India
March 16, 2016
Q. How to calculate the anode cell ratio in CED? Please, I am preparing for an interview and I need a clear answer.bala subramanian M
private automobile company - chennai, tamil nadu, india
CED Bath: Why/How has Sodium Increased with no other changes?March 31, 2016
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.
- Pune, Maharashtra India
April 13, 2016
A. Na content increases due to carryover of alkaline cleaners from P.T. line. Rinse parts thoroughly.
- Nasik, Maharashtra, India
April 12, 2016
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
June 27, 2016
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
powder coating & C E D coatings - Pune, Maharastra, India
July 7, 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.
- Chennai, Tamilnadu, India
Hi. That sounded like "expert comment" to me. Thanks!
Ted Mooney, P.E. RET
Pine Beach, New Jersey
Striving to live "Aloha"
March 24, 2017
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
June 14, 2017
A. CHECK EARTHING.PRASHANT KUMAR
CEPL - PUNE,MAHARSHTRA,INDIA
Anode Cell Area CalculationOctober 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?
Also how to select the range of Rectifier?
Designer - India
November 27, 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 thisRohit Kumar
- Faridabad haryana ,india
Masking for CED CoatingJanuary 22, 2018
We'd like to mask the wheel rim knurling during CED process.
Please suggest any masking.
- Chennai, India
April 11, 2018
Q. Hi sir,
I am having one small doubt regarding dot contamination (like popping). This only comes at body c-zone area, that means nearby the anode location.
Note: our dip coating system.
NEROLAC - Bangalore,Karnataka & India
Ed. note: Please forward a photo of the problem to for posting here.
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