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"Misc. problems/defects in CED (cathodic electrodeposition) coating"

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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.

Suresh Nataraj
NEROLAC - Bangalore, Karnataka & India

Ed. note: Please forward a photo of the problem to for posting here.

CED coating defects

September 5, 2018

Q. Please explain the defects of CED coating.

sathish kumar
employee - india

"Electrocoating: a Guidebook for Finishers"
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September 2018

A. Hi cousin Sathish. More words please -- are you asking a previous poster to clarify the defects they reported so that you can help them? If so, thanks -- attempting to teach is perhaps the fastest way to learn -- but please be more explicit about which posting you are replying to.

If you are looking for help yourself, you can read this thread, as well as threads 23154, 38297, 51966, and 57561. You can search the site using the term "CED defect" for many more threads on the topic.

You can also obtain the two books about CED coating which were suggested previously. I am not aware of training courses for this subject is India, but hopefully Coatec India [a finishing.com supporting advertiser] or a reader local to you will advise (please tell us your city because some areas of India probably aren't easily accessible to you). Best of luck, but be ready to invest at least a month of hard work in the study of CED defects :-)

Best of luck!


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

September 8, 2018

A. Dear Sathish, There are lots of defects in CED coating, as it's a very broad area.
But I will explain some defects which are usefully common for all CED Coating lines.
1) Paint Bubbles or CED bubbles :-
First of all CED is a continuous process. It's a non stoppable process. Whenever your conveyor getting stop this paint bubbles will come. this is a wet on wet process i.e. after dipping in ED bath it have mist spray to keep it wet, but some location are not covered in line, which show the Paint Bubbles issue.

D. Sharma
Paint Technologist - Aligarh,U.P., India

September 28, 2018

Q. We are doing E-coating for last 6 months and since last one week we are facing problems in the quality. Some lines appear after baking, and orange peel problems. The product doesn't have smooth finish, please help.

Ramakrishnan Iyer
Ganpath Electroplaters (Bombay) - Ludhiana-punjab, Indian

Ed. note: Photos to mooney@finishing.com would probably help, Ramakrishnan.

July 2, 2021

A. Dear sir
For line mark, check your phosphate bath turnover ratio /pump circulation capacity.

Ganesh sonone
Technical services - Aurangabad, India

December 2, 2018

Q. I'm using BASF ED paint. I'm facing a problem that high gloss level even I adjust the Pigment-Binder ratio.

- Chennai, Tamil Nadu, India

December 4, 2018

Q. Hi, my name is Harikishan. How to increase meq and conductivity of CED paint?

Hari kishan
Unique coater - Faridabad, haryana india

January 11, 2019

Q. I want to know CED coating defects and its solution.

Satyam auto - Kannauj,up, India

January 2019

A. Hi cousin Abhishek. If you can explain a specific defect, include photos, and give data about the prevailing situation that led to it, I'm sure the readers will be happy to try to help!

Otherwise you can study this posting and its photos and dialogs, the other thread it steers you to (thread 57561, "Pin holes in CED e-coating"), find many other threads on the subject by searching the site for "CED defects", and review the two books which we have mentioned on the subject, and search for your topic on surfacequery.com and scholar.google.com. It's unlikely that anyone is going to write a general tome covering the whole subject of possible CED defects and make it available to us all for free. Good luck, and get back to us with the actual situation you are confronting. Thanks.


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

CED coating adheres to sheet metal but not if zinc coated

February 6, 2019

Q. Dear Sir,

My question is on Zinc coated parts coated in CED. When we CED coat on sheet metal after maintain all process parameter then the coated parts pass SST (960 Hrs.) and Adhesion test pass; but on Zinc coated parts coated in CED then the parts do not pass the Adhesion test or SST.


Alok Ranjan Pal
- Ghaziabad, Uttar pradesh, India

February 2019

? Hi Alok. When you say "zinc coated" do you mean hot dip galvanized? Is the metal properly zinc phosphatized after the galvanizing?


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

March 26, 2019

Q. Hello sir,
We are struggling the problems on Pretreatment and Electrode deposition process. After completing this process we are facing so many problems like lints, air packs, E.D. drifts, flow marks, ash marks, etc. So anyone can please give me any solution for this problem. And give some parameters on E.D. paint.

Manikumar Surisetty
Paint shop - Andhra pradesh, India

September 14, 2019

Q. Dear sir, after giving the coating in our bath, the coating is coming on half the tank. Conductivity of our anolyte is 1.500 and ED tank temperature .38

Himanshu Srivastav
- Fridabad harayanan india

September 2019

A. Hi Fridabad. More words and details please! I'm not even sure if you are saying that the vat which is holding your bath contents is getting paint deposited onto half of it or whether the product you are coating is some kind of motorcycle fuel tank or similar and is being left half bare. Thanks.


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

CED e-coating bubbles/holes? Defect problem on chrome plated surface

January 18, 2020

Q. Hello Dear,

I'm custom finish coater.
I'm also trying to do some cathodic electrophoresis process (applied over nickel and chrome plated small objects like door handles, etc.).

I'm facing problem as in images, during epd coating (in epd tank) I get finish that has many Little little bubbles like inside it. Those micro bubbles are like in surface.

My process:
Degrease alkali
DI Rinse 2x
Acid pickle
DI Rinse 2x
Epd tank
DI Rinse 2x

I believe my substrate is okay because nothing happens in powder coating process so I believe nothing should happen in e-coat either.

Rafal Kolbu
- Brwinow, poland

January 2020

A. Hi Rafal. We did not get any images/photos; please e-mail them to mooney@finishing.com.

D. Sharma suggests above that a line stoppage is a common cause of this problem. Can you tell us whether the defect happens all the time or only some of the time? Chrome plating is not meant to be e-coated to my knowledge. Are you sure that you have good, functional, adhesion on the chrome?


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

January 18, 2020

Q. Hello,

That happens all time

I got detail movement in-tank. Chrome look Good, also I tried stress relief before e-coat too and that did not work.

Have no idea what is that, because it looks like something tiny air inside or maybe it's something else.

I tried different temp, voltage snd time setting.

I tried also powder coating same detail - for that everything is okay. Only e-coat goes bad.

On raw aluminium plate I also get that strange effect.
In touch that surface is smooth but has that small dot everywhere appearance

I wonder what steps should I take to find out problem?

I'm sending defects photos to my post.

32574-5a   32574-5c   32574-5b  

Thank You

Best Regards,

Rafal Kolbu [returning]
- Brwinow, poland

February 25, 2020

? Does this happen when you paint un-plated steel? I have seen where certain plated parts will outgas when e-coated.

Dan Mack
- Horicon, Wisconsin

March 17, 2020

Q. It happens on raw steel too.

Rafal kolbu [returning]
- Brwinow poland

August 1, 2020

Q. We are having Patches in CED Coating. Please suggest some remedy.


Upinder Singh
- Ludhiana Punjab

August 2020

thumbs up sign Hi Upinder. Thanks for the photo, but even with it I still doubt that anyone will be able to help you with no data supplied yet ... but we'll see.

Luck & Regards,

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

September 21, 2020

A. Dear Upinder Singh,
It seems that your parts are "RUSTY" before coating & you have to clean the rust.

Avinash Vidhate
- Nashik, Mahatashtra, INDIA

September 11, 2021

A. The part was not cleaned properly, due to which such a problem has come, clean it and load it.

Ajay Verma
Line supervisor - Faridabad, India

September 28, 2020

Ed. note: Please!
No abstract questions.

Q. We are experiencing difficulties in CED coating of inside of square steel tubing. Is this common problem with CED and what is causing it?

Bogdan K.
- WINNIPEG, Manitoba, Canada

September 2020

A. Hi Bogdan. It could be as simple as air in the tubing, or no solution transfer meaning that what is in the tube gets exhausted, or they could just be too long. I think we'll need some dimensions, data, explanation of what you mean by 'difficulties', etc. Thanks.

Luck & Regards,

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

CED part Quality Defect

October 28, 2020

Q. After CED Coating, have kept at oven around 175 degrees, when comes to Quality check we have found some paint dents, craters.

Its a Zinc plated part but no Passivation. Running the plan with the NVM of 14%, conductivity of 985.

CED coating has fisheyes 32574-7c CED coating has fisheyes 32574-7a CED coating has dents 32574-7b

Kindly suggest what's best to be done over the issue.

Sundaravanan Meganathan
- Chennai TAMIL NADU, India

November 3, 2020

A. Dear Sundaravanan Meganathan,
This seems to be FISH EYE problem. Go through fish eye problem on internet and you will find the answer.

Avinash Vidhate
- Nashik Maharashtra India

December 28, 2020

Q. Dear Sir

We are having a problem with CED coating. Our coating supplier always said the problem is coming from the material. However, it is not happening for 1 type of material but it happened in different material such as S55C and SPFH. We also unable to identify the actual defect on this CED coating. I am involving in metal stamping for automotive part. Hopefully, any expert in this finishing industry can help me to solve this problem. This defect really affects my production productivity.

32574-8a   32574-8b

32574-8d   32574-8c


Sulaini A. Rahman
- Selangor, Malaysia

March 5, 2021

A. Is this defect seen right after coating or after baking?
It might be due to temperature if it's after baking.

Amar Joshi
- noida india

March 5, 2021

Q. Hello I am Amar I am currently doing Cathodic electro coating (Ecoat)
Clear and Coloured one for jewelry and other mid sized items but the issue is I am getting wire marks on the product which seems to get rejected by the customer even though it's a small line
Currently using 0.3mm wire with typical coating spec 30 V 60 SEC 150 ° oven (have change a few specs but no positive so far) . Would really appreciate some advice on how to not get the mark.
Thank you

Amar joshi
- Noida India

March 6, 2021

Q. We are facing problem of shade variation in electrocolour (black colour). A little brownish colour obtained in every lot at same place (bottom side of bath) every time. what are possible reasons and solutions?

sandesh Raj
- aurangabad maharashtra india

April 11, 2021

A. Dear sandesh
check DFT on both surface. Brownish shade will give less DFT.
Shade variation depends on:
1. Non volAtile material concentration. add Resin & pigment as per ratio. Ask supplier for ratio.
2. Set Voltage- Increase voltage & observe current.
3. Number of Parts loading, shape & loading position - change loading position ,if more parts loaded then Decrease parts quantity.
4. Number of anode working. Confirm anolyte circulation.
5. Ensure properly burned jigs used for good contact.

vishal ghawate
- Pune ,India

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