Metal finishing Q&As since 1989
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Misc. problems/defects in CED (cathodic electrodeposition) coating
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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
April 11, 2018
Ed. note: Please forward a photo of the problem to mooney@finishing.com for posting here.
CED coating defects
Q. Please explain the defects of CED coating.
sathish kumaremployee - India
September 5, 2018
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
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 hopefully get access to the books about CED coating which we suggest ⇨
I am not aware of training courses for this subject is India, but hopefully 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 into the study of CED defects :-)
Best of luck!
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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.
Paint Technologist - Aligarh,U.P., India
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 IyerGanpath Electroplaters (Bombay) - Ludhiana-Punjab, Indian
September 28, 2018
Ed. note: Please forward photo of the problem to mooney@finishing.com for posting here.
A. Dear sir
For line mark, check your phosphate bath turnover ratio /pump circulation capacity.
Technical services - Aurangabad, India
July 2, 2021
Q. I'm using BASF ED paint. I'm facing a problem that high gloss level even I adjust the Pigment-Binder ratio.
ASHOKBABU A- Chennai, Tamil Nadu, India
December 2, 2018
Q. Hi, my name is Harikishan. How to increase meq and conductivity of CED paint?
Hari kishanUnique coater - Faridabad, haryana India
December 4, 2018
Q. I want to know CED coating defects and its solution.
ABHISHEK SinghSatyam auto - Kannauj,up, India
January 11, 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.
Regards,
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
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
- Ghaziabad, Uttar pradesh, India
February 6, 2019
? Hi Alok. When you say "zinc coated" do you mean hot dip galvanized? Is the metal properly zinc phosphatized after the galvanizing?
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
A. Hi, I feel the zinc coated part coating thickness is also contributing in this. Please check how much GSM it should be.
V GaneshkumarEngineer - Chennai, India
May 23, 2022
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.
Paint shop - Andhra pradesh, India
March 26, 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 14, 2019
A. Hi Fridabad. More words and details please! I'm not 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.
Regards,
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
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
Cure
I believe my substrate is okay because nothing happens in powder coating process so I believe nothing should happen in e-coat either.
- Brwinow, poland
January 18, 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?
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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.
Thank You
Best Regards,
Rafal
- Brwinow, poland
? 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
Q. It happens on raw steel too.
Rafal kolbu [returning]- Brwinow poland
Q. We are having Patches in CED Coating. Please suggest some remedy.
- Ludhiana Punjab
August 1, 2020
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,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
A. Dear Upinder Singh,
It seems that your parts are "RUSTY" before coating & you have to clean the rust.
- Nashik, Mahatashtra, INDIA
A. The part was not cleaned properly, due to which such a problem has come, clean it and load it.
Ajay VermaLine supervisor - Faridabad, India
September 11, 2021
⇦ (tip: readers rarely show interest in abstract questions, but people's actual situations usually prompt responses) 
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 28, 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,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
CED part Quality Defect
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.
Kindly suggest what's best to be done over the issue.
Sundaravanan Meganathan- Chennai TAMIL NADU, India
October 28, 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.
- Nashik Maharashtra India
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.
- Selangor, Malaysia
December 28, 2020
A. Is this defect seen right after coating or after baking?
It might be due to temperature if it's after baking.
- noida India
March 5, 2021
A. Hi,
Sulaini A. Rahman: This problem occurred due to sheet surface defects called "pitting"; complain to your Raw material supplier and definitely it will resolve.
Thanks.
Paintshop - Jaipur
April 29, 2022
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
- Noida India
March 5, 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
March 6, 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.
- Pune , India
Q. What is the function of anode cell. Someone tell me.
Ajay VermaLine supervisor - Faridabad, India
September 6, 2021
A. Dear Ajay Varma,
Greetings,
Its Functions are to act as an opposing electrode to the product being painted and to remove the acid continuously released by the paint during the deposition process.
Process incharge - Fharidabad [India]
Q. My name is ashuyashu. I have a doubt in our CED process:
1) sheet metal comes problem patches issue
2) after phosphating part is dry and rust observed
These two problems lasting 6 months. Please help me.
Student - Karnataka
September 26, 2021
Q. In ED painting voltage dropping
Example: 180V we set but actual 80V.
employee - Chennai, India
March 2, 2022
Q. Dear all, I am facing an ash mark issue on parts.
The part after CED and rinsing is found to be powdery after clearing off the water with air sprayer. The sensation of the surface of part is similar to touching powdered chalk.
We faced this issue just before the chiller was malfunctioning, causing the temperature of CED tank dropped to 20-22 °C for about 8 hours. I wonder if this event will cause irreversible damage to the CED tank?
Or this defect is more likely to be caused by pre-treatment line like impurities in acid etching and zinc phosphate tank?
- Skudai Johor, Malaysia
May 28, 2022
Q. In Aluminum Casted and Machined components CED coated surface is not smooth and has dull finish. While doing reworking after coating removal some of the components become military green and after re-coating aesthetically not okay, others which gives natural aluminum finish becomes okay after coating.
Please suggest suitable remedy.
Vishwa DeepQuality Manager - Noida UP India
July 11, 2023
A. Hi Vishwa. Are you sure they were not 'military green' before you started (from chromate conversion coating)? Are the components different grades of aluminum? What are they stripped with? Is the main problem just the reworks not working well, or do you have a substantial number of rejects the first time around?
What is your pretreatment sequence? After stripping will the components be pretreated again or are you CED coating raw non-pretreated aluminum?
I am afraid that there may not be enough information in your posting yet to do much but mislead you :-(
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. Hi all, I am a newbie in CED coating. I am getting some problems with it. I pretreat aluminium profile bar with concentrated caustic soda solution, so that the solution attacked onto the Al surface and created some tiny holes on it. Please instruct me how to level these holes or cover it after CED coating without defects remaining in appearance.
Jame Pieshop employee - Vietnam
August 3, 2023
A. Hi Jame,
I might be misunderstanding you, but holes in the aluminum substrate are not a CED problem, and I don't think they can be solved with CED coating. If this is one single item, perhaps the holes/pits can be filled with body filler, and the item then painted or powder coated.
If your pretreatment process is causing pits or holes you must fix the pretreatment process. It is never really satisfactory for a factory to plate, paint, or powder coat pitted items.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. After baking paint brightness appearance is dull.
Also temp. is under specification.
- Jounpur, up, India
September 14, 2023
A. Hi Goutam,
The temperature of what is "under specification"? The baking oven? Why aren't you fixing that? Sorry but I can't understand your brief question. More words please.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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. Hello everyone, kindly I would like to ask if you have ever experienced with CED and problem about rusty anodes?
We face a problem that our anolyte is totally rusty, containing 100-800 mg/l iron and it creates foam in the anolyte box. During summer maintenance we replaced totally rusty anodes but the iron still comes out, so we have to change anolyte weekly. What can be the cause of this? And why does it foam? The foam is very light and flies easily, can it be hydrogen foam ?
- Slovakia
September 24, 2023
Q. Dear sir,
I am new for CED coating process, I want to learn troubleshooting. Can you suggest?
- Hosur TN, India
November 10, 2023
Q. Hi, lately I am assigned to do research and development on CED. And lately my result is something like this picture.
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
Employee - Indonesia, Jawa Timur
January 12, 2024
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